Random access in new radio (NR) and other beamforming systems

ABSTRACT

A wireless transmit/receive unit (WTRU) may receive, from a base station, a synchronization signal/physical broadcast channel (SS/PBCH) block transmission. The WTRU may transmit using a physical random access channel (PRACH) resource. Further, the PRACH resource may be determined based on an SS/PBCH block index. Also, the SS/PBCH block index may be determined based on information associated with the SS/PBCH block transmission. In a further example, the information associated with the PBCH block may be derived from a demodulation reference signal (DMRS) sequence. In another example, the DMRS sequence may be a PBCH DMRS sequence. Also, the information associated with the PBCH block may be derived from PBCH payload bits. Further, the SS/PBCH block index may be associated with a beam. In addition, SS/PBCH transmissions of different beams may be transmitted at different times. Further, the PRACH resource may include a preamble resource, a time resource and a frequency resource.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.17/085,903, filed Oct. 30, 2020, which is a continuation of U.S. patentapplication Ser. No. 16/337,057, filed Mar. 27, 2019, which is based onthe U.S. National Stage, under 35 U.S.C. § 371, of InternationalApplication No. PCT/US2017/054086, filed Sep. 28, 2017, which claims thebenefit of U.S. Provisional Application No. 62/400,980 filed Sep. 28,2016, U.S. Provisional Application No. 62/416,592 filed Nov. 2, 2016,U.S. Provisional Application No. 62/443,319 filed Jan. 6, 2017 and U.S.Provisional Application No. 62/454,470 filed Feb. 3, 2017, the contentsof which are hereby incorporated by reference herein.

BACKGROUND

Several groups, including the International Telecommunications Union(ITU) Radio communication Sector (ITU-R), the Next Generation MobileNetworks (NGMN) Alliance and the 3rd Generation Partnership Project(3GPP) have set out general requirements for emerging 5th Generation(5G) systems, which may also be known as New Radio (NR). Based on thesegeneral requirements, a broad classification of the use cases for theemerging 5G systems can be depicted as follows: Enhanced MobileBroadband (eMBB), Massive Machine Type Communications (mMTC) and UltraReliable and Low latency Communications (URLLC).

Different use cases may focus on different requirements such as higherdata rate, higher spectrum efficiency, low power and higher energyefficiency, lower latency and higher reliability. A wide range ofspectrum bands ranging from 700 megahertz (MHz) to 80 gigahertz (GHz)are being considered for a variety of deployment scenarios.

It is known that as a carrier frequency increases, the severe path lossbecomes a crucial limitation to guarantee the sufficient coverage area.Transmission in millimeter wave systems could additionally suffer fromnon-line-of-sight losses, for example, diffraction loss, penetrationloss, oxygen absorption loss, foliage loss and the like.

SUMMARY

A method and system for determining a beam reciprocity for a beam of awireless transmit/receive unit (WTRU) are disclosed. A WTRU maydetermine a downlink (DL) beam for synchronization. Then, the WTRU maydetermine transmission reception point (TRP) transmit (TX)/receive (RX)beam correspondence information (BCI) using the determined DL beam.Further, the WTRU may determine a number of WTRU TX beams based on atleast the TRP TX/RX BCI. Also, the WTRU may determine a set of WTRU TXbeams based on at least the DL beam and the TRP TX/RX BCI, whereindetermining the set includes determining one or more WTRU TX beamdirections. In addition, the WTRU may transmit data using the determinedset of WTRU TX beams.

In an example, the determination of the TRP TX/RX BCI may be based on areceived TRP TX/RX BCI. In another example, the determination of the TRPTX/RX BCI may be based on at least one of a de-masking of a new radio(NR)-physical broadcast channel (PBCH) cyclic redundancy check (CRC)mask, one or more NR-PBCH resources, a NR-PBCH payload or a systeminformation block (SIB).

In a further example, the determined DL beam may be for NR-PBCHreception from a TRP. In an additional example, the NR-PBCH may be anSS/PBCH. Also, the SS/PBCH may include an SS block time index.

In addition, the TX/RX BCI may include at least one of an indication ofa correspondence type, a TX/RX beam width relationship or a TX/RX beamdirection relationship. Also, the determination of the set of WTRU TXbeams may be further based on the determined number of WTRU TX beams.

In an additional example, the WTRU may determine a preamble for a randomaccess channel (RACH) procedure based on resources used by thedetermined DL beam. The WTRU may then to transmit the preamble. In anexample, the preamble may be transmitted using preamble time resourcesmapped to a gNB RX beam.

In an example, a WTRU may receive, from a base station, informationconcerning an association between synchronization signal/PBCH (SS/PBCH)block transmissions and physical random access channel (PRACH)resources. In an example, each SS/PBCH block transmission may beassociated with a transmission beam of the base station. The WTRU mayreceive the SS/PBCH block transmissions and select one of thetransmissions. Further, the WTRU may compare a reference signal receivedpower (RSRP) associated with the selected transmission to a threshold.The WTRU may then determine between performing a random access procedureof a first type and a second type based on the comparison. Also, theWTRU may select a PRACH resource based on the selected transmission andthe information concerning the association between the transmissions andthe PRACH resources. Moreover, the WTRU may transmit a PRACH preamble,for the determined random access procedure, using the selected PRACHresource.

In a further example, the random access procedure of the first type maybe a two-step random access procedure and the random access procedure ofthe second type may be a four-step random access procedure. Also, thetwo-step random access procedure may include a first step includingtransmitting a physical uplink shared channel (PUSCH) transmission and asecond step including receiving a message in a control channel searchspace. Further, wherein the PUSCH transmission may be a grant-less PUSCHtransmission. In addition, the PUSCH transmission may include a radioresource control (RRC) connection request. Moreover, the first step ofthe two-step random access procedure further may include transmitting arandom access preamble. In another example, the four-step random accessprocedure may include a first step including transmitting a randomaccess preamble, a second step including receiving a random accessresponse, a third step including transmitting a PUSCH transmission and afourth step including receiving a contention resolution message.

In an additional example, the plurality of PRACH resources may includeone or more of PRACH preambles, time resources and frequency resources.Also, the WTRU may determine an SS/PBCH block time index for theselected transmission. Further, the WTRU may determine a transmissionbeam for uplink transmission based on the selected SS/PBCH blocktransmission. The PRACH preamble may be transmitted using the determinedtransmission beam.

In an example, a WTRU may receive an SS/PBCH transmission. The WTRU maydetermine an SS/PBCH block index based on information associated withthe SS/PBCH block transmission. Further, the WTRU may determine a PRACHresource based on the determined SS/PBCH block index. Also, the WTRU maytransmit a signal using the determined PRACH resource.

In a further example, the information associated with the PBCH block maybe derived from a demodulation reference signal (DMRS) sequence. Inanother example, the DMRS sequence may be a PBCH DMRS sequence. Also,the information associated with the PBCH block may be derived from PBCHpayload bits. Further, the SS/PBCH block index may be associated with abeam. In addition, SS/PBCH transmissions of different beams may betransmitted at different times.

BRIEF DESCRIPTION OF THE DRAWINGS

A more detailed understanding may be had from the following description,given by way of example in conjunction with the accompanying drawingswherein:

FIG. 1A is a system diagram of an example communications system in whichone or more disclosed embodiments may be implemented;

FIG. 1B is a system diagram of an example wireless transmit/receive unit(WTRU) that may be used within the communications system illustrated inFIG. 1A;

FIG. 1C is a system diagram illustrating an example radio access network(RAN) and an example core network (CN) that may be used within thecommunications system illustrated in FIG. 1A;

FIG. 1D is a system diagram illustrating a further example RAN and afurther example CN that may be used within the communications systemillustrated in FIG. 1A;

FIG. 2 is a flowchart diagram which illustrates an example of abeamformed random access method;

FIG. 3 is a flowchart diagram which illustrates an example method andprocedure for partial transmit (TX) beam/receive (RX) beam reciprocity;

FIG. 4 is a flowchart diagram which illustrates an example use ofreciprocity to determine a WTRU-TX beam set;

FIG. 5 is a flowchart diagram which illustrates an example method forthe indication of TX/RX beam reciprocity;

FIG. 6 is a flowchart diagram which illustrates an example method andprocedure to determine TX/RX beam reciprocity;

FIG. 7 is a flowchart diagram which illustrates another example methodfor the indication of TX/RX beam reciprocity;

FIG. 8 is a flowchart diagram which illustrates an example of a WTRUprocedure for a beam operation mode;

FIG. 9 is a flowchart diagram which illustrates an example WTRU methodand procedure for determining and reporting WTRU beam correspondence,beam reciprocity or both;

FIG. 10 is a flowchart diagram which illustrates an example PhysicalRandom Access Channel (PRACH) procedure and preamble format selectionbased on beam deployment;

FIG. 11 is a flowchart diagram which illustrates another example PRACHprocedure and preamble format selection;

FIG. 12 is a network operation diagram which illustrates a networkoperation mode with an energy saving mode WTRU;

FIG. 13 is a network operation diagram which illustrates a networkoperation mode with a low latency mode;

FIG. 14 is a network operation diagram which illustrates a networkoperation in energy saving mode and low latency mode;

FIG. 15 is a flowchart diagram which illustrates transmission receptionpoint (TRP) efficient operations and determining an operation mode; and

FIG. 16 is a flowchart diagram which illustrates an example method andprocedure for beam reciprocity based random access.

DETAILED DESCRIPTION

FIG. 1A is a diagram illustrating an example communications system 100in which one or more disclosed embodiments may be implemented. Thecommunications system 100 may be a multiple access system that providescontent, such as voice, data, video, messaging, broadcast, etc., tomultiple wireless users. The communications system 100 may enablemultiple wireless users to access such content through the sharing ofsystem resources, including wireless bandwidth. For example, thecommunications systems 100 may employ one or more channel accessmethods, such as code division multiple access (CDMA), time divisionmultiple access (TDMA), frequency division multiple access (FDMA),orthogonal FDMA (OFDMA), single-carrier FDMA (SC-FDMA), zero-tailunique-word DFT-Spread OFDM (ZT UW DTS-s OFDM), unique word OFDM(UW-OFDM), resource block-filtered OFDM, filter bank multicarrier(FBMC), and the like.

As shown in FIG. 1A, the communications system 100 may include wirelesstransmit/receive units (WTRUs) 102 a, 102 b, 102 c, 102 d, a radioaccess network (RAN) 104, a core network (CN) 106, a public switchedtelephone network (PSTN) 108, the Internet 110, and other networks 112,though it will be appreciated that the disclosed embodiments contemplateany number of WTRUs, base stations, networks, and/or network elements.Each of the WTRUs 102 a, 102 b, 102 c, 102 d may be any type of deviceconfigured to operate and/or communicate in a wireless environment. Byway of example, the WTRUs 102 a, 102 b, 102 c, 102 d, any of which maybe referred to as a station (STA), may be configured to transmit and/orreceive wireless signals and may include a user equipment (UE), a mobilestation, a fixed or mobile subscriber unit, a subscription-based unit, apager, a cellular telephone, a personal digital assistant (PDA), asmartphone, a laptop, a netbook, a personal computer, a wireless sensor,a hotspot or Mi-Fi device, an Internet of Things (IoT) device, a watchor other wearable, a head-mounted display (HMD), a vehicle, a drone, amedical device and applications (e.g., remote surgery), an industrialdevice and applications (e.g., a robot and/or other wireless devicesoperating in an industrial and/or an automated processing chaincontexts), a consumer electronics device, a device operating oncommercial and/or industrial wireless networks, and the like. Any of theWTRUs 102 a, 102 b, 102 c and 102 d may be interchangeably referred toas a UE.

The communications system 100 may also include a base station 114 aand/or a base station 114 b. Each of the base stations 114 a, 114 b maybe any type of device configured to wirelessly interface with at leastone of the WTRUs 102 a, 102 b, 102 c, 102 d to facilitate access to oneor more communication networks, such as the CN 106, the Internet 110,and/or the other networks 112. By way of example, the base stations 114a, 114 b may be a base transceiver station (BTS), a NodeB, an eNode B(eNB), a Home Node B, a Home eNode B, a next generation NodeB, such as agNode B (gNB), a new radio (NR) NodeB, a site controller, an accesspoint (AP), a wireless router, and the like. While the base stations 114a, 114 b are each depicted as a single element, it will be appreciatedthat the base stations 114 a, 114 b may include any number ofinterconnected base stations and/or network elements.

The base station 114 a may be part of the RAN 104, which may alsoinclude other base stations and/or network elements (not shown), such asa base station controller (BSC), a radio network controller (RNC), relaynodes, and the like. The base station 114 a and/or the base station 114b may be configured to transmit and/or receive wireless signals on oneor more carrier frequencies, which may be referred to as a cell (notshown). These frequencies may be in licensed spectrum, unlicensedspectrum, or a combination of licensed and unlicensed spectrum. A cellmay provide coverage for a wireless service to a specific geographicalarea that may be relatively fixed or that may change over time. The cellmay further be divided into cell sectors. For example, the cellassociated with the base station 114 a may be divided into threesectors. Thus, in one embodiment, the base station 114 a may includethree transceivers, i.e., one for each sector of the cell. In anembodiment, the base station 114 a may employ multiple-input multipleoutput (MIMO) technology and may utilize multiple transceivers for eachsector of the cell. For example, beamforming may be used to transmitand/or receive signals in desired spatial directions.

The base stations 114 a, 114 b may communicate with one or more of theWTRUs 102 a, 102 b, 102 c, 102 d over an air interface 116, which may beany suitable wireless communication link (e.g., radio frequency (RF),microwave, centimeter wave, micrometer wave, infrared (IR), ultraviolet(UV), visible light, etc.). The air interface 116 may be establishedusing any suitable radio access technology (RAT).

More specifically, as noted above, the communications system 100 may bea multiple access system and may employ one or more channel accessschemes, such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA, and the like. Forexample, the base station 114 a in the RAN 104 and the WTRUs 102 a, 102b, 102 c may implement a radio technology such as Universal MobileTelecommunications System (UMTS) Terrestrial Radio Access (UTRA), whichmay establish the air interface 116 using wideband CDMA (WCDMA). WCDMAmay include communication protocols such as High-Speed Packet Access(HSPA) and/or Evolved HSPA (HSPA+). HSPA may include High-Speed Downlink(DL) Packet Access (HSDPA) and/or High-Speed Uplink (UL) Packet Access(HSUPA).

In an embodiment, the base station 114 a and the WTRUs 102 a, 102 b, 102c may implement a radio technology such as Evolved UMTS TerrestrialRadio Access (E-UTRA), which may establish the air interface 116 usingLong Term Evolution (LTE) and/or LTE-Advanced (LTE-A) and/orLTE-Advanced Pro (LTE-A Pro).

In an embodiment, the base station 114 a and the WTRUs 102 a, 102 b, 102c may implement a radio technology such as NR Radio Access, which mayestablish the air interface 116 using NR.

In an embodiment, the base station 114 a and the WTRUs 102 a, 102 b, 102c may implement multiple radio access technologies. For example, thebase station 114 a and the WTRUs 102 a, 102 b, 102 c may implement LTEradio access and NR radio access together, for instance using dualconnectivity (DC) principles. Thus, the air interface utilized by WTRUs102 a, 102 b, 102 c may be characterized by multiple types of radioaccess technologies and/or transmissions sent to/from multiple types ofbase stations (e.g., an eNB and a gNB).

In other embodiments, the base station 114 a and the WTRUs 102 a, 102 b,102 c may implement radio technologies such as IEEE 802.11 (i.e.,Wireless Fidelity (WiFi), IEEE 802.16 (i.e., Worldwide Interoperabilityfor Microwave Access (WiMAX)), CDMA2000, CDMA2000 1×, CDMA2000 EV-DO,Interim Standard 2000 (IS-2000), Interim Standard 95 (IS-95), InterimStandard 856 (IS-856), Global System for Mobile communications (GSM),Enhanced Data rates for GSM Evolution (EDGE), GSM EDGE (GERAN), and thelike.

The base station 114 b in FIG. 1A may be a wireless router, Home Node B,Home eNode B, or access point, for example, and may utilize any suitableRAT for facilitating wireless connectivity in a localized area, such asa place of business, a home, a vehicle, a campus, an industrialfacility, an air corridor (e.g., for use by drones), a roadway, and thelike. In one embodiment, the base station 114 b and the WTRUs 102 c, 102d may implement a radio technology such as IEEE 802.11 to establish awireless local area network (WLAN). In an embodiment, the base station114 b and the WTRUs 102 c, 102 d may implement a radio technology suchas IEEE 802.15 to establish a wireless personal area network (WPAN). Inyet another embodiment, the base station 114 b and the WTRUs 102 c, 102d may utilize a cellular-based RAT (e.g., WCDMA, CDMA2000, GSM, LTE,LTE-A, LTE-A Pro, NR etc.) to establish a picocell or femtocell. Asshown in FIG. 1A, the base station 114 b may have a direct connection tothe Internet 110. Thus, the base station 114 b may not be required toaccess the Internet 110 via the CN 106.

The RAN 104 may be in communication with the CN 106, which may be anytype of network configured to provide voice, data, applications, and/orvoice over internet protocol (VoIP) services to one or more of the WTRUs102 a, 102 b, 102 c, 102 d. The data may have varying quality of service(QoS) requirements, such as differing throughput requirements, latencyrequirements, error tolerance requirements, reliability requirements,data throughput requirements, mobility requirements, and the like. TheCN 106 may provide call control, billing services, mobile location-basedservices, pre-paid calling, Internet connectivity, video distribution,etc., and/or perform high-level security functions, such as userauthentication. Although not shown in FIG. 1A, it will be appreciatedthat the RAN 104 and/or the CN 106 may be in direct or indirectcommunication with other RANs that employ the same RAT as the RAN 104 ora different RAT. For example, in addition to being connected to the RAN104, which may be utilizing a NR radio technology, the CN 106 may alsobe in communication with another RAN (not shown) employing a GSM, UMTS,CDMA 2000, WiMAX, E-UTRA, or WiFi radio technology.

The CN 106 may also serve as a gateway for the WTRUs 102 a, 102 b, 102c, 102 d to access the PSTN 108, the Internet 110, and/or the othernetworks 112. The PSTN 108 may include circuit-switched telephonenetworks that provide plain old telephone service (POTS). The Internet110 may include a global system of interconnected computer networks anddevices that use common communication protocols, such as thetransmission control protocol (TCP), user datagram protocol (UDP) and/orthe internet protocol (IP) in the TCP/IP internet protocol suite. Thenetworks 112 may include wired and/or wireless communications networksowned and/or operated by other service providers. For example, thenetworks 112 may include another CN connected to one or more RANs, whichmay employ the same RAT as the RAN 104 or a different RAT.

Some or all of the WTRUs 102 a, 102 b, 102 c, 102 d in thecommunications system 100 may include multi-mode capabilities (e.g., theWTRUs 102 a, 102 b, 102 c, 102 d may include multiple transceivers forcommunicating with different wireless networks over different wirelesslinks). For example, the WTRU 102 c shown in FIG. 1A may be configuredto communicate with the base station 114 a, which may employ acellular-based radio technology, and with the base station 114 b, whichmay employ an IEEE 802 radio technology.

FIG. 1B is a system diagram illustrating an example WTRU 102. As shownin FIG. 1B, the WTRU 102 may include a processor 118, a transceiver 120,a transmit/receive element 122, a speaker/microphone 124, a keypad 126,a display/touchpad 128, non-removable memory 130, removable memory 132,a power source 134, a global positioning system (GPS) chipset 136,and/or other peripherals 138, among others. It will be appreciated thatthe WTRU 102 may include any sub-combination of the foregoing elementswhile remaining consistent with an embodiment.

The processor 118 may be a general purpose processor, a special purposeprocessor, a conventional processor, a digital signal processor (DSP), aplurality of microprocessors, one or more microprocessors in associationwith a DSP core, a controller, a microcontroller, Application SpecificIntegrated Circuits (ASICs), Field Programmable Gate Arrays (FPGAs), anyother type of integrated circuit (IC), a state machine, and the like.The processor 118 may perform signal coding, data processing, powercontrol, input/output processing, and/or any other functionality thatenables the WTRU 102 to operate in a wireless environment. The processor118 may be coupled to the transceiver 120, which may be coupled to thetransmit/receive element 122. While FIG. 1B depicts the processor 118and the transceiver 120 as separate components, it will be appreciatedthat the processor 118 and the transceiver 120 may be integratedtogether in an electronic package or chip.

The transmit/receive element 122 may be configured to transmit signalsto, or receive signals from, a base station (e.g., the base station 114a) over the air interface 116. For example, in one embodiment, thetransmit/receive element 122 may be an antenna configured to transmitand/or receive RF signals. In an embodiment, the transmit/receiveelement 122 may be an emitter/detector configured to transmit and/orreceive IR, UV, or visible light signals, for example. In yet anotherembodiment, the transmit/receive element 122 may be configured totransmit and/or receive both RF and light signals. It will beappreciated that the transmit/receive element 122 may be configured totransmit and/or receive any combination of wireless signals.

Although the transmit/receive element 122 is depicted in FIG. 1B as asingle element, the WTRU 102 may include any number of transmit/receiveelements 122. More specifically, the WTRU 102 may employ MIMOtechnology. Thus, in one embodiment, the WTRU 102 may include two ormore transmit/receive elements 122 (e.g., multiple antennas) fortransmitting and receiving wireless signals over the air interface 116.

The transceiver 120 may be configured to modulate the signals that areto be transmitted by the transmit/receive element 122 and to demodulatethe signals that are received by the transmit/receive element 122. Asnoted above, the WTRU 102 may have multi-mode capabilities. Thus, thetransceiver 120 may include multiple transceivers for enabling the WTRU102 to communicate via multiple RATs, such as NR and IEEE 802.11, forexample.

The processor 118 of the WTRU 102 may be coupled to, and may receiveuser input data from, the speaker/microphone 124, the keypad 126, and/orthe display/touchpad 128 (e.g., a liquid crystal display (LCD) displayunit or organic light-emitting diode (OLED) display unit). The processor118 may also output user data to the speaker/microphone 124, the keypad126, and/or the display/touchpad 128. In addition, the processor 118 mayaccess information from, and store data in, any type of suitable memory,such as the non-removable memory 130 and/or the removable memory 132.The non-removable memory 130 may include random-access memory (RAM),read-only memory (ROM), a hard disk, or any other type of memory storagedevice. The removable memory 132 may include a subscriber identitymodule (SIM) card, a memory stick, a secure digital (SD) memory card,and the like. In other embodiments, the processor 118 may accessinformation from, and store data in, memory that is not physicallylocated on the WTRU 102, such as on a server or a home computer (notshown).

The processor 118 may receive power from the power source 134, and maybe configured to distribute and/or control the power to the othercomponents in the WTRU 102. The power source 134 may be any suitabledevice for powering the WTRU 102. For example, the power source 134 mayinclude one or more dry cell batteries (e.g., nickel-cadmium (NiCd),nickel-zinc (NiZn), nickel metal hydride (NiMH), lithium-ion (Li-ion),etc.), solar cells, fuel cells, and the like.

The processor 118 may also be coupled to the GPS chipset 136, which maybe configured to provide location information (e.g., longitude andlatitude) regarding the current location of the WTRU 102. In additionto, or in lieu of, the information from the GPS chipset 136, the WTRU102 may receive location information over the air interface 116 from abase station (e.g., base stations 114 a, 114 b) and/or determine itslocation based on the timing of the signals being received from two ormore nearby base stations. It will be appreciated that the WTRU 102 mayacquire location information by way of any suitablelocation-determination method while remaining consistent with anembodiment.

The processor 118 may further be coupled to other peripherals 138, whichmay include one or more software and/or hardware modules that provideadditional features, functionality and/or wired or wirelessconnectivity. For example, the peripherals 138 may include anaccelerometer, an e-compass, a satellite transceiver, a digital camera(for photographs and/or video), a universal serial bus (USB) port, avibration device, a television transceiver, a hands free headset, aBluetooth® module, a frequency modulated (FM) radio unit, a digitalmusic player, a media player, a video game player module, an Internetbrowser, a Virtual Reality and/or Augmented Reality (VR/AR) device, anactivity tracker, and the like. The peripherals 138 may include one ormore sensors. The sensors may be one or more of a gyroscope, anaccelerometer, a hall effect sensor, a magnetometer, an orientationsensor, a proximity sensor, a temperature sensor, a time sensor; ageolocation sensor, an altimeter, a light sensor, a touch sensor, amagnetometer, a barometer, a gesture sensor, a biometric sensor, ahumidity sensor and the like.

The WTRU 102 may include a full duplex radio for which transmission andreception of some or all of the signals (e.g., associated withparticular subframes for both the UL (e.g., for transmission) and DL(e.g., for reception) may be concurrent and/or simultaneous. The fullduplex radio may include an interference management unit to reduce andor substantially eliminate self-interference via either hardware (e.g.,a choke) or signal processing via a processor (e.g., a separateprocessor (not shown) or via processor 118). In an embodiment, the WTRU102 may include a half-duplex radio for which transmission and receptionof some or all of the signals (e.g., associated with particularsubframes for either the UL (e.g., for transmission) or the DL (e.g.,for reception)).

FIG. 1C is a system diagram illustrating the communication system 100including a RAN 113 and a CN 115. As noted above, the RAN 113 may employan E-UTRA radio technology to communicate with the WTRUs 102 a, 102 b,102 c over the air interface 116. The RAN 113 may also be incommunication with the CN 115.

The RAN 113 may include eNode-Bs 160 a, 160 b, 160 c, though it will beappreciated that the RAN 113 may include any number of eNode-Bs whileremaining consistent with an embodiment. The eNode-Bs 160 a, 160 b, 160c may each include one or more transceivers for communicating with theWTRUs 102 a, 102 b, 102 c over the air interface 116. In one embodiment,the eNode-Bs 160 a, 160 b, 160 c may implement MIMO technology. Thus,the eNode-B 160 a, for example, may use multiple antennas to transmitwireless signals to, and/or receive wireless signals from, the WTRU 102a.

Each of the eNode-Bs 160 a, 160 b, 160 c may be associated with aparticular cell (not shown) and may be configured to handle radioresource management decisions, handover decisions, scheduling of usersin the UL and/or DL, and the like. As shown in FIG. 1C, the eNode-Bs 160a, 160 b, 160 c may communicate with one another over an X2 interface.

The CN 115 shown in FIG. 1C may include a mobility management entity(MME) 162, a serving gateway (SGW) 164, and a packet data network (PDN)gateway (PGW) 166. While the foregoing elements are depicted as part ofthe CN 115, it will be appreciated that any of these elements may beowned and/or operated by an entity other than the CN operator.

The MME 162 may be connected to each of the eNode-Bs 162 a, 162 b, 162 cin the RAN 113 via an S1 interface and may serve as a control node. Forexample, the MME 162 may be responsible for authenticating users of theWTRUs 102 a, 102 b, 102 c, bearer activation/deactivation, selecting aparticular serving gateway during an initial attach of the WTRUs 102 a,102 b, 102 c, and the like. The MME 162 may provide a control planefunction for switching between the RAN 113 and other RANs (not shown)that employ other radio technologies, such as GSM and/or WCDMA.

The SGW 164 may be connected to each of the eNode Bs 160 a, 160 b, 160 cin the RAN 113 via the S1 interface. The SGW 164 may generally route andforward user data packets to/from the WTRUs 102 a, 102 b, 102 c. The SGW164 may perform other functions, such as anchoring user planes duringinter-eNode B handovers, triggering paging when DL data is available forthe WTRUs 102 a, 102 b, 102 c, managing and storing contexts of theWTRUs 102 a, 102 b, 102 c, and the like.

The SGW 164 may be connected to the PGW 166, which may provide the WTRUs102 a, 102 b, 102 c with access to packet-switched networks, such as theInternet 110, to facilitate communications between the WTRUs 102 a, 102b, 102 c and IP-enabled devices.

The CN 115 may facilitate communications with other networks. Forexample, the CN 115 may provide the WTRUs 102 a, 102 b, 102 c withaccess to circuit-switched networks, such as the PSTN 108, to facilitatecommunications between the WTRUs 102 a, 102 b, 102 c and traditionalland-line communications devices. For example, the CN 115 may include,or may communicate with, an IP gateway (e.g., an IP multimedia subsystem(IMS) server) that serves as an interface between the CN 115 and thePSTN 108. In addition, the CN 115 may provide the WTRUs 102 a, 102 b,102 c with access to the other networks 112, which may include otherwired and/or wireless networks that are owned and/or operated by otherservice providers.

Although the WTRU is described in FIGS. 1A-1D as a wireless terminal, itis contemplated that in certain representative embodiments that such aterminal may use (e.g., temporarily or permanently) wired communicationinterfaces with the communication network.

In representative embodiments, the other network 112 may be a WLAN.

A WLAN in Infrastructure Basic Service Set (BSS) mode may have an AccessPoint (AP) for the BSS and one or more stations (STAs) associated withthe AP. The AP may have access or an interface to a Distribution System(DS) or another type of wired/wireless network that carries traffic into and/or out of the BSS. Traffic to STAs that originates from outsidethe BSS may arrive through the AP and may be delivered to the STAs.Traffic originating from STAs to destinations outside the BSS may besent to the AP to be delivered to respective destinations. Trafficbetween STAs within the BSS may be sent through the AP, for example,where the source STA may send traffic to the AP and the AP may deliverthe traffic to the destination STA. The traffic between STAs within aBSS may be considered and/or referred to as peer-to-peer traffic. Thepeer-to-peer traffic may be sent between (e.g., directly between) thesource and destination STAs with a direct link setup (DLS). In certainrepresentative embodiments, the DLS may use an 802.11e DLS or an 802.11ztunneled DLS (TDLS). A WLAN using an Independent BSS (IBSS) mode may nothave an AP, and the STAs (e.g., all of the STAs) within or using theIBSS may communicate directly with each other. The IBSS mode ofcommunication may sometimes be referred to herein as an “ad-hoc” mode ofcommunication.

When using the 802.11ac infrastructure mode of operation or a similarmode of operations, the AP may transmit a beacon on a fixed channel,such as a primary channel. The primary channel may be a fixed width(e.g., 20 MHz wide bandwidth) or a dynamically set width. The primarychannel may be the operating channel of the BSS and may be used by theSTAs to establish a connection with the AP. In certain representativeembodiments, Carrier Sense Multiple Access with Collision Avoidance(CSMA/CA) may be implemented, for example in 802.11 systems. ForCSMA/CA, the STAs (e.g., every STA), including the AP, may sense theprimary channel. If the primary channel is sensed/detected and/ordetermined to be busy by a particular STA, the particular STA may backoff. One STA (e.g., only one station) may transmit at any given time ina given BSS.

High Throughput (HT) STAs may use a 40 MHz wide channel forcommunication, for example, via a combination of the primary 20 MHzchannel with an adjacent or nonadjacent 20 MHz channel to form a 40 MHzwide channel.

Very High Throughput (VHT) STAs may support 20 MHz, 40 MHz, 80 MHz,and/or 160 MHz wide channels. The 40 MHz, and/or 80 MHz, channels may beformed by combining contiguous 20 MHz channels. A 160 MHz channel may beformed by combining 8 contiguous 20 MHz channels, or by combining twonon-contiguous 80 MHz channels, which may be referred to as an 80+80configuration. For the 80+80 configuration, the data, after channelencoding, may be passed through a segment parser that may divide thedata into two streams. Inverse Fast Fourier Transform (IFFT) processing,and time domain processing, may be done on each stream separately. Thestreams may be mapped on to the two 80 MHz channels, and the data may betransmitted by a transmitting STA. At the receiver of the receiving STA,the above described operation for the 80+80 configuration may bereversed, and the combined data may be sent to the Medium Access Control(MAC).

Sub 1 GHz modes of operation are supported by 802.11af and 802.11ah. Thechannel operating bandwidths, and carriers, are reduced in 802.11af and802.11ah relative to those used in 802.11n, and 802.11ac. 802.11afsupports 5 MHz, 10 MHz, and 20 MHz bandwidths in the TV White Space(TVWS) spectrum, and 802.11ah supports 1 MHz, 2 MHz, 4 MHz, 8 MHz, and16 MHz bandwidths using non-TVWS spectrum. According to a representativeembodiment, 802.11ah may support Meter Type Control/Machine-TypeCommunications (MTC), such as MTC devices in a macro coverage area. MTCdevices may have certain capabilities, for example, limited capabilitiesincluding support for (e.g., only support for) certain and/or limitedbandwidths. The MTC devices may include a battery with a battery lifeabove a threshold (e.g., to maintain a very long battery life).

WLAN systems, which may support multiple channels, and channelbandwidths, such as 802.11n, 802.11ac, 802.11af, and 802.11ah, include achannel which may be designated as the primary channel. The primarychannel may have a bandwidth equal to the largest common operatingbandwidth supported by all STAs in the BSS. The bandwidth of the primarychannel may be set and/or limited by a STA, from among all STAs inoperating in a BSS, which supports the smallest bandwidth operatingmode. In the example of 802.11ah, the primary channel may be 1 MHz widefor STAs (e.g., MTC type devices) that support (e.g., only support) a 1MHz mode, even if the AP, and other STAs in the BSS support 2 MHz, 4MHz, 8 MHz, 16 MHz, and/or other channel bandwidth operating modes.Carrier sensing and/or Network Allocation Vector (NAV) settings maydepend on the status of the primary channel. If the primary channel isbusy, for example, due to a STA (which supports only a 1 MHz operatingmode) transmitting to the AP, all available frequency bands may beconsidered busy even though a majority of the available frequency bandsremains idle.

In the United States, the available frequency bands, which may be usedby 802.11ah, are from 902 MHz to 928 MHz. In Korea, the availablefrequency bands are from 917.5 MHz to 923.5 MHz. In Japan, the availablefrequency bands are from 916.5 MHz to 927.5 MHz. The total bandwidthavailable for 802.11ah is 6 MHz to 26 MHz depending on the country code.

FIG. 1D is a system diagram illustrating the communication system 100including a RAN 117 and a CN 119. As noted above, the RAN 117 may employan NR radio technology to communicate with the WTRUs 102 a, 102 b, 102 cover the air interface 116. The RAN 117 may also be in communicationwith the CN 119.

The RAN 117 may include gNBs 180 a, 180 b, 180 c, though it will beappreciated that the RAN 117 may include any number of gNBs whileremaining consistent with an embodiment. The gNBs 180 a, 180 b, 180 cmay each include one or more transceivers for communicating with theWTRUs 102 a, 102 b, 102 c over the air interface 116. In one embodiment,the gNBs 180 a, 180 b, 180 c may implement MIMO technology. For example,gNBs 180 a, 108 b may utilize beamforming to transmit signals to and/orreceive signals from the gNBs 180 a, 180 b, 180 c. Thus, the gNB 180 a,for example, may use multiple antennas to transmit wireless signals to,and/or receive wireless signals from, the WTRU 102 a. In an embodiment,the gNBs 180 a, 180 b, 180 c may implement carrier aggregationtechnology. For example, the gNB 180 a may transmit multiple componentcarriers to the WTRU 102 a (not shown). A subset of these componentcarriers may be on unlicensed spectrum while the remaining componentcarriers may be on licensed spectrum. In an embodiment, the gNBs 180 a,180 b, 180 c may implement Coordinated Multi-Point (CoMP) technology.For example, WTRU 102 a may receive coordinated transmissions from gNB180 a and gNB 180 b (and/or gNB 180 c).

The WTRUs 102 a, 102 b, 102 c may communicate with gNBs 180 a, 180 b,180 c using transmissions associated with a scalable numerology. Forexample, the OFDM symbol spacing and/or OFDM subcarrier spacing may varyfor different transmissions, different cells, and/or different portionsof the wireless transmission spectrum. The WTRUs 102 a, 102 b, 102 c maycommunicate with gNBs 180 a, 180 b, 180 c using subframe or transmissiontime intervals (TTIs) of various or scalable lengths (e.g., containing avarying number of OFDM symbols and/or lasting varying lengths ofabsolute time).

The gNBs 180 a, 180 b, 180 c may be configured to communicate with theWTRUs 102 a, 102 b, 102 c in a standalone configuration and/or anon-standalone configuration. In the standalone configuration, WTRUs 102a, 102 b, 102 c may communicate with gNBs 180 a, 180 b, 180 c withoutalso accessing other RANs (e.g., such as eNode-Bs 160 a, 160 b, 160 c).In the standalone configuration, WTRUs 102 a, 102 b, 102 c may utilizeone or more of gNBs 180 a, 180 b, 180 c as a mobility anchor point. Inthe standalone configuration, WTRUs 102 a, 102 b, 102 c may communicatewith gNBs 180 a, 180 b, 180 c using signals in an unlicensed band. In anon-standalone configuration WTRUs 102 a, 102 b, 102 c may communicatewith/connect to gNBs 180 a, 180 b, 180 c while also communicatingwith/connecting to another RAN such as eNode-Bs 160 a, 160 b, 160 c. Forexample, WTRUs 102 a, 102 b, 102 c may implement DC principles tocommunicate with one or more gNBs 180 a, 180 b, 180 c and one or moreeNode-Bs 160 a, 160 b, 160 c substantially simultaneously. In thenon-standalone configuration, eNode-Bs 160 a, 160 b, 160 c may serve asa mobility anchor for WTRUs 102 a, 102 b, 102 c and gNBs 180 a, 180 b,180 c may provide additional coverage and/or throughput for servicingWTRUs 102 a, 102 b, 102 c.

Each of the gNBs 180 a, 180 b, 180 c may be associated with a particularcell (not shown) and may be configured to handle radio resourcemanagement decisions, handover decisions, scheduling of users in the ULand/or DL, support of network slicing, DC, interworking between NR andE-UTRA, routing of user plane data towards User Plane Function (UPF) 184a, 184 b, routing of control plane information towards Access andMobility Management Function (AMF) 182 a, 182 b and the like. As shownin FIG. 1D, the gNBs 180 a, 180 b, 180 c may communicate with oneanother over an Xn interface.

The CN 119 shown in FIG. 1D may include at least one AMF 182 a, 182 b,at least one UPF 184 a,184 b, at least one Session Management Function(SMF) 183 a, 183 b, and possibly a Data Network (DN) 185 a, 185 b. Whilethe foregoing elements are depicted as part of the CN 119, it will beappreciated that any of these elements may be owned and/or operated byan entity other than the CN operator.

The AMF 182 a, 182 b may be connected to one or more of the gNBs 180 a,180 b, 180 c in the RAN 117 via an N2 interface and may serve as acontrol node. For example, the AMF 182 a, 182 b may be responsible forauthenticating users of the WTRUs 102 a, 102 b, 102 c, support fornetwork slicing (e.g., handling of different protocol data unit (PDU)sessions with different requirements), selecting a particular SMF 183 a,183 b, management of the registration area, termination of non-accessstratum (NAS) signaling, mobility management, and the like. Networkslicing may be used by the AMF 182 a, 182 b in order to customize CNsupport for WTRUs 102 a, 102 b, 102 c based on the types of servicesbeing utilized WTRUs 102 a, 102 b, 102 c. For example, different networkslices may be established for different use cases such as servicesrelying on ultra-reliable low latency (URLLC) access, services relyingon enhanced massive mobile broadband (eMBB) access, services for MTCaccess, and the like. The AMF 182 a, 182 b may provide a control planefunction for switching between the RAN 117 and other RANs (not shown)that employ other radio technologies, such as LTE, LTE-A, LTE-A Pro,and/or non-3GPP access technologies such as WiFi.

The SMF 183 a, 183 b may be connected to an AMF 182 a, 182 b in the CN119 via an N11 interface. The SMF 183 a, 183 b may also be connected toa UPF 184 a, 184 b in the CN 119 via an N4 interface. The SMF 183 a, 183b may select and control the UPF 184 a, 184 b and configure the routingof traffic through the UPF 184 a, 184 b. The SMF 183 a, 183 b mayperform other functions, such as managing and allocating UE IP address,managing PDU sessions, controlling policy enforcement and QoS, providingDL data notifications, and the like. A PDU session type may be IP-based,non-IP based, Ethernet-based, and the like.

The UPF 184 a, 184 b may be connected to one or more of the gNBs 180 a,180 b, 180 c in the RAN 117 via an N3 interface, which may provide theWTRUs 102 a, 102 b, 102 c with access to packet-switched networks, suchas the Internet 110, to facilitate communications between the WTRUs 102a, 102 b, 102 c and IP-enabled devices. The UPF 184, 184 b may performother functions, such as routing and forwarding packets, enforcing userplane policies, supporting multi-homed PDU sessions, handling user planeQoS, buffering DL packets, providing mobility anchoring, and the like.

The CN 119 may facilitate communications with other networks. Forexample, the CN 119 may include, or may communicate with, an IP gateway(e.g., an IP multimedia subsystem (IMS) server) that serves as aninterface between the CN 119 and the PSTN 108. In addition, the CN 119may provide the WTRUs 102 a, 102 b, 102 c with access to the othernetworks 112, which may include other wired and/or wireless networksthat are owned and/or operated by other service providers. In oneembodiment, the WTRUs 102 a, 102 b, 102 c may be connected to a local DN185 a, 185 b through the UPF 184 a, 184 b via the N3 interface to theUPF 184 a, 184 b and an N6 interface between the UPF 184 a, 184 b andthe DN 185 a, 185 b.

In view of FIGS. 1A-1D, and the corresponding description of FIGS.1A-1D, one or more, or all, of the functions described herein withregard to one or more of: WTRU 102 a-d, Base Station 114 a-b, eNode-B160 a-c, MME 162, SGW 164, PGW 166, gNB 180 a-c, AMF 182 a-b, UPF 184a-b, SMF 183 a-b, DN 185 a-b, and/or any other device(s) describedherein, may be performed by one or more emulation devices (not shown).The emulation devices may be one or more devices configured to emulateone or more, or all, of the functions described herein. For example, theemulation devices may be used to test other devices and/or to simulatenetwork and/or WTRU functions.

The emulation devices may be designed to implement one or more tests ofother devices in a lab environment and/or in an operator networkenvironment. For example, the one or more emulation devices may performthe one or more, or all, functions while being fully or partiallyimplemented and/or deployed as part of a wired and/or wirelesscommunication network in order to test other devices within thecommunication network. The one or more emulation devices may perform theone or more, or all, functions while being temporarilyimplemented/deployed as part of a wired and/or wireless communicationnetwork. The emulation device may be directly coupled to another devicefor purposes of testing and/or performing testing using over-the-airwireless communications.

The one or more emulation devices may perform the one or more, includingall, functions while not being implemented/deployed as part of a wiredand/or wireless communication network. For example, the emulationdevices may be utilized in a testing scenario in a testing laboratoryand/or a non-deployed (e.g., testing) wired and/or wirelesscommunication network in order to implement testing of one or morecomponents. The one or more emulation devices may be test equipment.Direct RF coupling and/or wireless communications via RF circuitry(e.g., which may include one or more antennas) may be used by theemulation devices to transmit and/or receive data.

Based on the general requirements set out by the InternationalTelecommunications Union (ITU) Radiocommunication Sector (ITU-R), theNext Generation Mobile Networks (NGMN) Alliance and the 3^(rd)Generation Partnership Project (3GPP), a broad classification of the usecases for emerging 5th Generation (5G) systems can be depicted asfollows: Enhanced Mobile Broadband (eMBB), Massive Machine TypeCommunications (mMTC) and Ultra Reliable and Low latency Communications(URLLC). Different use cases may focus on different requirements such ashigher data rate, higher spectrum efficiency, low power and higherenergy efficiency, lower latency and higher reliability. A wide range ofspectrum bands ranging from 700 megahertz (MHz) to 80 gigahertz (GHz)are being considered for a variety of deployment scenarios.

It is known that as a carrier frequency increases, the severe path lossbecomes a crucial limitation to guarantee the sufficient coverage area.Transmission in millimeter wave systems could additionally suffer fromnon-line-of-sight losses, for example, diffraction loss, penetrationloss, oxygen absorption loss, foliage loss, and the like. Utilizingdozens or even hundreds of antenna elements to generate a beam formedsignal is an effective way to compensate the severe path loss byproviding significant beam forming gain. Beamforming techniques mayinclude digital, analog and hybrid beamforming.

An eNode-B (or eNB) and/or a WTRU may use a random access procedure forat least one of: WTRU initial access, for example, to a cell or eNode-B;reset of UL timing, for example to reset or align WTRU uplink (UL)timing with respect to a certain cell; and reset of timing duringhandover, for example to reset or align WTRU timing with respect to thehandover target cell. The WTRU may transmit a certain physical randomaccess channel (PRACH) preamble sequence at a certain power, PPRACH,which may be based on configured parameters and/or measurements, and theWTRU may transmit the preamble using a certain time-frequency resourceor resources. The configured parameters, which may be provided orconfigured by the eNode-B, may include one or more of: initial preamblepower, for example, preamblelnitialReceivedTargetPower; a preambleformat based offset, for example, deltaPreamble; a random accessresponse (RAR) window, for example, ra-ResponseWindowSize; a powerramping factor, for example, powerRampingStep; and a maximum number ofretransmissions, for example, preambleTransMax. The PRACH resources,which may include preambles or sets of preambles and/or time/frequencyresources which may be used for preamble transmission, may be providedor configured by the eNode-B. The measurements may include pathloss. Oneor more the time-frequency resources may be chosen by the WTRU from anallowed set or may be chosen by the eNode-B and signalled to the WTRU.

Following WTRU transmission of a preamble, if the eNode-B detects thepreamble, it may respond with an RAR message. If the WTRU may not ordoes not receive an RAR message for the transmitted preamble, which mayfor example, correspond to a certain preamble index and/ortime/frequency resource, within an allotted time, for example, ara-ResponseWindowSize, the WTRU may send another preamble at a latertime, at a higher power, for example, higher than the previous preambletransmission by powerRampingStep, where the transmission power may belimited by a maximum power, for example a WTRU configured maximum powerwhich may be for the WTRU as a whole, for example PCMAX, or for acertain serving cell of the WTRU, for example PCMAX,c. The WTRU may waitagain for receipt of an RAR message from the eNode-B. This sequence oftransmitting and waiting may continue until the eNode-B may respond withan RAR message or until the maximum number of random access preambletransmissions, for example, preambleTransMax, may have been reached. TheeNode-B may transmit and the WTRU may receive the RAR message inresponse to a single preamble transmission.

A particular instance of a random access procedure may becontention-based or contention-free. A contention-free procedure may beinitiated by a request, for example from an eNode-B, which may, forexample, be via physical layer signalling such as a physical downlinkcontrol channel (PDCCH) order or by higher layer signalling such as aradio resource control (RRC) reconfiguration message, for example, anRRC connection reconfiguration message, which may include mobilitycontrol information and may, for example, indicate or correspond to ahandover request. For a contention-free procedure which may be initiatedby PDCCH order in subframe n, the PRACH preamble may be transmitted inthe first subframe or the first subframe available for PRACH n+k2 wherek2 may be >=6. When initiated by an RRC command, there may be otherdelays which may be specified, for example, there may be minimum and/ormaximum required or allowed delays. The WTRU may autonomously initiate acontention-based procedure for reasons which may include for example,initial access, restoration of UL synchronization, or recovering fromradio link failure. For certain events, for example, events other thanrecovery from radio link failure, it may not be defined or specified asto how long after such an event the WTRU may send the PRACH preamble.

For a contention-free random access (RA) procedure, a network-signalledPRACH preamble may be used, for example, by a WTRU. For acontention-based random access procedure, the WTRU may autonomouslychoose a preamble where the preamble format and/or the one or moretime/frequency resources available for preamble transmissions may bebased on an indication or index, for example, prach-configIndex, whichmay be provided or signalled by the eNode-B.

One of the preambles transmitted at the progressively higher transmitpowers may be detected by the eNode-B. An RAR message may be sent by theeNode-B in response to that one detected preamble.

A PRACH preamble may be considered a PRACH resource in the examplespresented herein. For example, PRACH resources may include a PRACHpreamble, time, and/or frequency resources.

The terms preamble resource, RACH resource and PRACH resource may beused interchangeably in the examples provided herein. Further, the termsRA, RACH, and PRACH may be used interchangeably in the examplespresented herein. Also, Beam reciprocity and beam correspondence may beinterchangeable in the examples presented herein.

As disclosed herein, various examples are presented for use in physicalrandom access in beamforming systems. The following problems areaddressed herein. In 5G New Radio (NR), it may be desirable to design aunified RACH for both single and multi-beam operations. Also, in NR itmay be desirable to incorporate transmit (TX)/receive (RX) reciprocityproperties into random access design. Further, in NR it may be desirableto have efficient solutions to configure PRACH resources. In addition,in a multiple transmission reception point (TRP) scenario, methods forreceiving an RAR message or performing random access channel (RACH)reception from a single TRP and/or multiple TRPs are provided herein.Moreover, in NR, it may be desirable to design a simplified RACH ascompared to conventional RACH used in LTE.

Modified WTRU procedures may be needed to handle TX/RX beam reciprocitywhen full, partial or no reciprocity for TX/RX beam reciprocity ispresent. When TX/RX beams are reciprocal, association may be used toexplore reciprocity. A next generation NodeB (gNB) or a TRP may changean order of a beam sweep. In this case, an association or link may beoverridden. A TRP may be used as a non-limiting an example of a cell ornode that may have a communication path for transmission, for example,in the downlink, and/or reception, for example, in the uplink, with aWTRU.

As used herein, the terms cell, eNode-B, gNB, TRP, node, and entity maybe used interchangeably. Further, the terms indication, indicator, andinformation may be used interchangeably herein. Also, the examplesdescribed herein for a TRP may be applied to a WTRU and those describedfor a WTRU may be applied to a TRP and still be consistent with otherexamples described herein. The terms same direction and reciprocaldirection may be substituted for each other and still be consistent withthe examples provided herein. In examples provided herein, the termreciprocal direction may be used to represent a direction that isopposite, for example, plus or minus 180 degrees from, anotherdirection. For a WTRU, a beam direction may be from the perspective ofthe WTRU. For a TRP, a beam direction may be from the perspective of theTRP. As used in examples provided herein, the terms beam reciprocity andbeam correspondence may be used interchangeably. Further, in examplesprovided herein, the terms beam reciprocity information and beamcorrespondence information (BCI) may be used interchangeably. Further,the terms DL beam, gNB TX beam and WTRU RX beam may be usedinterchangeably in examples provided herein. In addition, the terms ULbeam, gNB RX beam and WTRU TX beam may be used interchangeably inexamples provided herein.

Also, the terms mode and state may be used interchangeably in examplesprovided herein. Further connected mode may be RRC connected mode in theexamples provided herein. Moreover, the terms RA resources and physicalRA (PRA) resources may be used interchangeably in examples providedherein. Further, the terms synchronization signal (SS) block andSS/physical broadcast channel (PBCH) block may be used interchangeablyin examples provided herein. In addition, the terms PBCH and NR-PBCH maybe used interchangeably in examples provided herein, and the terms SSand NR-SS may be used interchangeably in examples provided herein.

When TX/RX beams are partially reciprocal, a partial association or apartial link may be used to explore partial reciprocity. Some gNB TXbeams may not be reciprocal to the gNB RX beams. For example, TXbeamwidth may not be equal to RX beamwidth. This may be due to differenttransmit and receive antenna structures or different numbers ofantennas. Therefore the following two cases may need to be consideredfor WTRU procedures. In one case, the gNB TX beamwidth may be greaterthan the gNB RX beamwidth. In another case, the gNB TX beamwidth may beless than the gNB RX beamwidth.

In another scenario, the gNB TX beam may not be completely aligned withthe RX beam. For example, the TX and the RX beams may partially overlapeven if they have the same beamwidth.

In a case when TX/RX beams are not reciprocal, dynamic association maybe used. Modified methods for indication of gNB RX beams from gNB TXbeams are needed. A dynamic indication or a semi-static indication maybe used.

An example method may include transmitting, by a gNB, an indication of agNB TX/RX reciprocity. The method may further comprise determining, by agNB, a mapping of a gNB TX beam to a gNB RX beam. A gNB may determineone or more WTRU transmit beams and transmit an indication, to a WTRU,of a best DL beam for a RAR. A mapping of TX and RX beams may be furtherrefined. On a condition a gNB TX/RX reciprocity is present, a fullassociation between a gNB and a WTRU may be established.

Also, an example method may include performing TX beam sweeping andreceiving, from a TRP, information corresponding to a selected WTRU TXbeam, wherein the selected WTRU beam information is based on adetermined WTRU TX beam. The WTRU may be further configured to performRX beam sweeping and determine, one or more RX beams based on ameasurement criteria. The WTRU may derive one or more TX beams using thedetermined one or more RX beams and the WTRU may determine beamreciprocity based on a set of rules.

An example system may include a receiver configured to receive, from aTRP, a request for the WTRU to determine beam correspondence orreciprocity information. Based on the received request, circuitry may beconfigured to determine a beam correspondence or reciprocity. The systemfurther includes a transmitter configured to transmit, to the TRP, aWTRU capability indication comprising both WTRU capability informationand information corresponding to the determined beam correspondence orreciprocity. In this way, a single message may be utilized for bothcapability indication and beam correspondence or reciprocity.

FIG. 2 is a flowchart diagram which illustrates an example of abeamformed random access method. As shown in flowchart diagram 200, thefollowing example procedures may be perform. A gNB may transmit and aWTRU may receive an indication of gNB TX beam/RX beam reciprocity 210.Further, a WTRU may map a gNB TX beam to a gNB RX beam 220. In addition,the WTRU may determine the WTRU transmit beam or beams 230. Also, theWTRU may transmit and gNB may receive an indication of the best DL beamfor RAR 240. The WTRU may then refine mappings of TX and RX beams 250.

Example methods of handling gNB TX beam/RX beam reciprocity aredescribed herein. If gNB TX/RX reciprocity is present, full associationbetween one or more TX beams and one or more Rx beams of gNB as well asassociation between WTRU and a gNB may be established. A one-to-onemapping between a SS/PBCH block including PBCH and PRACH time-beamresources may be used. One or more PRACH time resources may be used toindicate the detected SS/PBCH blocks. Association may indicate the bestpreamble RX beam at the gNB from a detected best SS/PBCH block or PBCHTX beam. That is, a TX beam may be equal to an RX beam.

A PBCH may signal the TX/RX beam reciprocity mode to the WTRU. When WTRUreceives this message, WTRU may need to perform preamble transmissionfor one particular gNB RX beam or for each of the gNB RX beams tocooperate with a gNB RX beam sweep. A TX/RX beam reciprocity mode may beused. For example, TX/RX beam reciprocity mode=“1” may indicate thatTX/RX beam reciprocity is present. In a further example, TX/RX beamreciprocity mode=“0” may indicate that TX/RX beam reciprocity is absent.

In an example TX/RX beam reciprocity mode, such as in TX/RX beamreciprocity mode=“1”, a gNB may change the beam sweep order and overridethe beam order for beam sweep at any time due to the flexible operationof the system and the network. A gNB may override the association andTX/RX reciprocity. In this case there may be no indication about thebest preamble RX beam from the detected best SS/PBCH block including aPBCH TX beam. In an example, the timing of the RX beam and the timing ofthe TX beam are synchronous but the beam order may not be synchronouseven though TX/RX beam reciprocity may be present. Therefore a full RXbeam sweep may be necessary regardless of the existence of TX/RX beamreciprocity.

In a further example, the gNB may send an indication to the WTRUincluding information regarding an association between SS/PBCH blocksand one or more PRACH preamble sequences and/or one or more resources.For example, the gNB may signal WTRU to transmit the preamble inparticular time resources for the gNB RX beam. By doing so, the WTRU maynot need to perform a preamble transmission for all gNB RX beams duringthe gNB RX beam sweep period. A PBCH or broadcast signal/channelcarrying remaining minimum system information or other systeminformation may be used to indicate such information about the best gNBRX beam to the WTRU. The gNB may send such an indication in a furtherexample TX/RX beam reciprocity mode, such as TX/RX beam reciprocitymode=“0” or similar mode. The mode may be used in order to have the WTRUsave power.

An example method is proposed herein to override the association and theTX/RX beam reciprocity. In an example, a solution is to indicate theoverride Mode. For example, a PBCH may signal the override mode to aWTRU. When the WTRU receives this message, the WTRU may need to performpreamble transmission for each gNB RX beam or a subset of gNB RX beamsto cooperate with a gNB RX beam sweep.

In an example, an override mode=“0” may indicate no information about agNB RX beam should be assumed even though TX/RX beam reciprocityMode=“1”. An override mode=“1” may indicate information about a gNB RXbeam may be assumed if TX/RX beam reciprocity mode=“1”. In anotherexample, method, an association mode=“0” may indicate no informationabout the gNB RX beam and an assumption should be made from a gNB TXbeam. Further, an association mode=“1” may indicate information aboutthe gNB RX beam may be assumed from the gNB TX beam.

A gNB may have control of an override and have knowledge about TX/RXbeam reciprocity. Therefore, a gNB may signal an association mode to aWTRU. In an example, if association mode=“0”, no information about a gNBRX beam may be assumed even though TX/RX beams have reciprocity. Inanother example, when association mode=“1”, information about a gNB RXbeam may be assumed, even though TX/RX Beams have no reciprocity.

Example methods of handling partial gNB TX/RX beam reciprocity or no gNBTX/RX beam reciprocity are discussed herein. If TX/RX reciprocity ispartially present, partial association such as one-to-many, many-to-one,many-to-many may be used. Association may still indicate the bestpreamble RX beam at the gNB from the detected best PBCH TX beam as longas association is time synchronous. In this case, the gNB may need toarrange the RX beam to match the TX beam as much as possible.

TX and RX beamwidths may be different due to no gNB TX/RX beamreciprocity or partial TX/RX beam reciprocity. If an RX beam is widerand fully covers the TX beam, such a wide RX beam may be sufficient toreceive a preamble transmission. If the RX beam is narrower and coversonly part of a TX beam, a better resolution of the RX beam may beneeded. In an example, more symbols may be needed for a gNB RX beamsweep. For example, if an RX beam is only half of a TX beam inbeamwidth, the gNB may need to double the beam sweep resolution for gNBreceiver. Therefore a non-uniform beam sweep may be proposed forpreamble transmission and/or reception. A PBCH may use M-beams for a TXbeam sweep while preamble reception at the gNB may use L-beams for abeam sweep. When L>M, RX beamwidth may be smaller than TX beamwidth.When L<M, RX beamwidth may be larger than TX beamwidth.

In examples described herein, TX beams and RX beams may be partiallyoverlapping. In an example, even when a TX beamwidth and an RX beamwidthare the same but the TX beam and the RX beam are not fully aligned witheach other, then two or more RX beams may be needed for beam sweep inorder to cover the best TX beam, due to the beam overlap between the TXand RX beams. A different number of beams for TX and RX beam sweep maybe needed as in the case of a TX beamwidth being different from an RXbeamwidth. However the gNB may need to monitor left and right beamscorresponding to a detected DL beam for a given WTRU. In an example,beam receive diversity with signal combining may be used.

Association may be used to explore TX/RX reciprocity. When reciprocityis not present, full association may become less important. In anexample, partial association may be used. That is, one DL TX beam may bemapped to two or multiple UL RX beams if DL TX beam is wider. Ormultiple DL TX beams may be mapped to one UL RX beams if DL TX beam isnarrower. There could be a case where multiple DL TX beams may be mappedto multiple UL RX beams, such as in a case when the TX beamwidth is notan integer multiple of RX beamwidth or vice-versa.

If TX/RX beam reciprocity is not present, dynamic signaling orsemi-static signaling may be used. In an example, a time order of thebeams may be present but at least one of the following may also holdtrue: the TX beam resolution may not be the same as the RX beamresolution, the TX beam and the RX beam may not be aligned or and the TXbeam and the RX beam may not be synchronous. In a further example, abeam order may not be present, and a TX beamwidth may not be equal to anRX beamwidth. An RX beam sweep may be necessary. However, a solutionusing PBCH to indicate the desired RX beam to WTRU may be required. Anexample solution is illustrated in FIG. 3 .

FIG. 3 is a flowchart diagram which illustrates an example method andprocedure for partial TX beam/RX beam reciprocity. In an example shownin flowchart diagram 300, a resolution for TX beamwidth and a resolutionfor RX beamwidth may be determined 310. Also, a TX beam and RX beamoverlapping ratio may be determined 320. Further, a correspondingsignaling mechanism may be chosen for indicating the beamwidthresolution as well as beam overlapping ratio 330. For example, the gNBmay signal association information between one or more SS/PBCH blocksand one or more PRACH preamble sequences and/or one or moretime/frequency resources to a WTRU. For example, the gNB may signal beamcorrespondence information to a WTRU. In addition, a gNB may decide andchoose an RX beam sweeping strategy for a gNB receiver 340. As well, aTX beam sweeping strategy for a WTRU transmitter, may be decided andchosen by the gNB 350. In an example, the gNB may choose that the WTRUshould use a preamble transmission as a beam sweeping strategy.

A WTRU may receive a synchronization (SYNC) signal, reference signal,and/or other signal from a TRP, in order to, for example, synchronize intime and/or frequency with the TRP. A WTRU may receive one or moresignals or information from a TRP in a direction that may be, forexample, may be determined by the WTRU to be, an acceptable direction ora best direction. An acceptable direction may be a direction from whichthe WTRU may be able to receive and/or decode one or more signals fromthe TRP, such as a broadcast signal that may include a broadcast channel(BCH), for example, a PBCH. A best direction may be a direction that theWTRU may determine to provide the highest signal strength (or other bestmeasure or measurement), for example, from among a set of acceptabledirections.

The determined direction may correspond to a TRP transmit (TRP-TX) beam.Further, the determined direction may correspond to a WTRU receive(WTRU-RX) beam. Information regarding the TRP-TX beam may be providedexplicitly, for example, via a PBCH or system information that may bebroadcast, or implicitly for example, by the use of different syncsignals or reference signals for different beams or by the use ofdifferent masking or cover codes on the sync signals or referencesignals to distinguish different beams.

A WTRU may determine a receive direction based on the directiongranularity of its WTRU-RX beams which may or may not match thegranularity of the TRP-TX beams. In an example, the receive directionmay be an angle of arrival.

A WTRU may choose or determine a set of transmit beams (WTRU-TX beams)or transmit directions for a transmission, for example, an initialtransmission, to a TRP based on a determined acceptable beam ordirection or a determined best beam or direction. Direction and beam maybe substituted for each other in the embodiments and examples describedherein.

In an example, reciprocity information may be provided, for example, bya TRP, and/or used for example, by a WTRU. A WTRU may determine a set ofbeams or directions for transmission to a TRP based on at leastreciprocity, for example, information regarding reciprocity, of the TRPtransmit and receive beams, directions, and/or communication paths.

A WTRU may receive and/or use a configuration or information regardingreciprocity that may be used or assumed for a cell, an eNode-B, a gNB, aTRP, a node, for example, a network node, or another entity. In anexample, another entity may be a network entity with which the WTRU maycommunicate.

The reciprocity information, for example, for a TRP, may be used toindicate the relation between a transmit communication path and areceive communication path, for example, of the TRP. For example, thereciprocity information may include an indication of a relationshipbetween a TRP-TX beam characteristic and a TRP-RX beam characteristic.

A beam characteristic may be a beam width, a beam direction, and/or anumber of beams. For example, reciprocity information for a TRP mayindicate at least one of the following. The reciprocity information mayindicate whether a TRP-RX beam width is wider, or narrower, than atransmit beam width. Also, the reciprocity information may indicatewhether the number of TRP-TX beams and TRP-RX beams is the same.

Further, the reciprocity information may indicate whether a TRP-RX beamdirection is the same as a TRP-TX beam direction. In an additionalexample, the reciprocity information may indicate whether each TRP-RXbeam direction is the same as a respective TRP-TX beam direction. In anexample, the reciprocity information may indicate whether the beamdirections are the same regardless of whether the number of beams is thesame and/or the beam widths are the same.

Also, the reciprocity information may indicate whether the TRP has aTRP-RX beam in the same direction as a transmit beam. Moreover, in anexample, the reciprocity information may indicate whether each TRP-RXbeam of the TRP has the same direction as a respective transmit beam.

A transmit beam, for example, for which reciprocity information may beindicated, may be a beam that may provide at least one of asynchronization signal, a reference signal, a broadcast channel orsignal, for example, a PBCH, and/or system information, for example, asystem information block (SIB). Further, a transmit beam, for example,for which reciprocity information may be indicated, may refer to a beamthat may provide at least one of a synchronization signal, a referencesignal, a broadcast channel or signal, for example, a PBCH, and/orsystem information, for example, a SIB.

A reciprocity indication may provide a value, a ratio, and/or an indexto a table of values that may convey the relevant information. One ormore reciprocity indications may be provided via broadcast or systeminformation. One or more reciprocity indications may be provided by aPBCH. A WTRU may receive and/or determine reciprocity information andmay use the information, for example, at least one reciprocityindicator, to determine at least one beam characteristic fortransmission to a TRP.

A transmission may be of a signal, for example, a reference signal, orchannel. A transmission may be of a preamble, data or a data channel,control information or a control channel. A transmission may be for aninitial access which may be a random access, a grant-less access, or agranted access. In an example, random access may include that a preamblefor transmission may be chosen randomly. In a further example, a grantedaccess may include a scheduled access.

A WTRU may determine a beam, according to an example described herein,that may be an acceptable beam or a best beam. In an example, anacceptable beam may include an acceptable direction for the beam and abest beam may include the best direction for the beam. In the examplesdescribed herein, the term determined DL beam is used as a non-limitingexample of a determined best beam or acceptable beam.

A WTRU may determine a set of M transmit beams (WTRU-TX beams) ortransmit directions for a transmission, for example, an initialtransmission, to a TRP based on at least reciprocity information or areciprocity indication it may receive or determine regarding the TRP.The WTRU may transmit to the TRP on the M transmit beams. Transmissionon multiple beams may be in series or in parallel, for example, based onthe capabilities of the WTRU and/or the TRP.

For example, a WTRU may determine the number of beams, M, in the set ofWTRU-TX beams based on at least reciprocity information or a reciprocityindication the WTRU may determine or receive. The WTRU may determinewhich WTRU-TX beams to include in the set, for example, on which beamsor in which directions to transmit, based on at least reciprocityinformation or a reciprocity indication the WTRU may determine orreceive.

The WTRU may determine the set of WTRU-TX beams, for example, based onreciprocity information, to include at least one of the following: afirst WTRU-TX beam, for example, one or only one WTRU-TX beam, that maybe in the same direction or a nearest direction as the determined DLbeam; one or more, for example, N, beams that may be adjacent to, forexample, left and/or right of, the first WTRU-TX beam.

In an example, N may be 0. The value of M and/or N may be dependent onwhether TRP-TX beams and TRP-RX beams may have the same direction, forexample, whether TRP-RX beams may be centered on TRP-TX beams.

For example, if TRP-RX beams may be centered on TRP-TX beams, N may be afirst number, such as 0 or a small number, and/or M may be a firstnumber such as 1 or a small number. If TRP-RX beams may not be centeredon TRP-TX beams, M and/or N may be a second number that may be largerthan the first corresponding number.

The value of M and/or N may be dependent on the beam width of at leastone of the WTRU-TX beams, the WTRU-RX beams, the TRP-TX beams, and/orthe TRP-RX beams. N may be an even number. N may be evenly split to theleft and right of the first beam.

WTRU-TX beam directions may not match exactly to WTRU-RX beam directionsor to TRP-TX beams. A WTRU-TX beam with a nearest direction to adetermined DL beam may be used as an UL beam.

A beam type may be at least one of a TRP-TX beam, a TRP-RX beam, aWTRU-TX beam, and/or a WTRU-RX beam. A WTRU may determine at least oneof M, N, and/or the set of WTRU-TX beams based on at least one of: thenumber of beams and/or beam widths of at least one beam type; or therelationship of the number of beams and/or beam widths between at leasttwo beam types.

For example, M may be determined to be a first number when the beamwidths of the TRP-TX beams and the TRP-RX beams may be the same. M maybe determined to be a second number when the beam widths of the TRP-TXbeams and the TRP-RX beams may not be the same. The second number may besmaller than the first number, for example when the TRP-RX beams may bewider than the TRP-TX beams.

The WTRU may determine a beam width for a WTRU-TX beam based on at leastreciprocity information the WTRU may receive.

For example, a WTRU may provide beam characteristic information and/orreciprocity information, for example, for WTRU-TX and WTRU-RX beams, toa TRP, for example, a TRP with which it may communicate. An example isshown in FIG. 4 .

FIG. 4 is a flowchart diagram which illustrates an example use ofreciprocity to determine a WTRU-TX beam set. In an example shown inflowchart diagram 400, a WTRU may determine a DL beam to use 410. Forexample, the WTRU may determine to use a best DL beam. In a furtherexample, the WTRU may determine to use an acceptable DL beam. The WTRUdetermination may be based on beam strength. In a further example, theDL beam may be used for synchronization between the WTRU and the TRP. Inanother example, the DL beam may be used by the WTRU for PBCH reception.Further, the WTRU may determine TRP beam reciprocity information. Forexample, the WTRU may determine TRP beam reciprocity information basedon the determined DL beam. In an example, the WTRU may receive TRP beamreciprocity information 420. As a result, the WTRU may determine TRPbeam reciprocity information based on the received TRP beam reciprocityinformation. In another example, the WTRU may be pre-configured with TRPbeam reciprocity information. In a further example, the WTRU maydetermine TRP beam reciprocity information based on a PBCH cyclicredundancy check (CRC) mask, one or more PBCH resources, a PBCH payload,a SIB, or the like. In addition, the WTRU may determine TRP TX/RX BCI.For example, the WTRU may determine the TRP BCI based on the determinedDL beam. In an example, the WTRU may receive TRP TX/RX BCI. As a result,the WTRU may determine TRP TX/RX BCI based on the received TRP TX/RXBCI. In another example, the WTRU may be pre-configured with TRP TX/RXBCI. In a further example, the WTRU may determine TRP TX/RX BCI based ona PBCH cyclic redundancy check (CRC) mask, one or more PBCH resources, aPBCH payload, a SIB, or the like.

Also, the WTRU may determine a number of WTRU-TX beams, which may berepresented by M, based on the beam reciprocity information 430. Inanother example, the WTRU may determine a number of WTRU-TX beams basedon the TRP TX/RX BCI. In addition, the WTRU may determine the WTRU-TXbeam set based on the beam reciprocity information 440. In a furtherexample, the WTRU may determine the WTRU-TX beam set based on the TRPTX/RX BCI. In still a further example, the WTRU determining the set ofWTRU-TX beams may be further based on the determined number of WTRU-TXbeams. In an example, determining the WTRU-TX beam set includesdetermining one or more WTRU-TX beam directions.

Moreover, the WTRU may transmit to the TRP using the determined WTRU-TXbeam set 450. In an example, the WTRU may transmit to the TRP using arandom access procedure. In a further example, the WTRU may transmitdata using the determined set of WTRU TX beams.

In a further example, the WTRU may determine a timing for transmissionusing the set of WTRU TX beams based on at least the TRP TX/RX BCI. Inanother example, the TRP TX/RX BCI may include at least one of anindication of a correspondence type, a TX/RX beam width relationship ora TX/RX beam direction relationship. In yet another example, the WTRUmay determine and transmit a WTRU TX/RX BCI.

A PBCH may indicate TX/RX reciprocity for optimizing preamble reception.Several methods may be used for the indication. For example, a CRC maskmay be used or employed in a such a method. Another example method mayuse an orthogonal cover code. A further example method may use a PBCHdetection position (such as time or frequency). An additional examplemethod may employ 1 or 2 bits explicitly in a PBCH payload.

FIG. 5 is a flowchart diagram which illustrates an example method forthe indication of TX/RX beam reciprocity. As shown in an example inflowchart diagram 500, TX/RX beam reciprocity may be indicated using aCRC mask via a PBCH. Depending on the number of TX/RX beam reciprocitymodes, a corresponding number of masks may be used. For example, a PBCHpayload may be first generated 510. Also, a CRC may be generated 530.The generated CRC may be masked with a sequence that is a function ofTX/RX reciprocity 550. PBCH payload may then be concatenated with themasked CRC 570.

In order to indicate three types of TX/RX beam reciprocity, threeconfigurations may be defined. For example, a configuration 1 mayindicate full TX/RX beam reciprocity, a configuration 2 may indicatepartial TX/RX beam reciprocity, and a configuration 3 may indicate noTX/RX beam reciprocity. The numbering of the configurations may bereordered and still be consistent with the examples provided herein.Further, different numbers of configurations may be used and still beconsistent with the examples provided herein.

In an example, three sequences may be used for the CRC mask for themethod depicted in FIG. 5 . In other examples, a different number ofsequences may be used for the CRC mask and still be consistent with theexamples provided herein.

In an example, partial TX/RX reciprocity may be due to interference andmay occur in a dynamic manner. Therefore, using a semi-static signalingmethod may not be an optimal procedure to provide a TX/RX beamreciprocity indication. Instead, a combination of semi-static anddynamic signaling method may be optimal. For example, in order toindicate two types of TX/RX beam reciprocity, two configuration typesmay be defined. In an example, configuration 1 may indicate full TX/RXreciprocity and configuration 2 may indicate no TX/RX reciprocity.Therefore two sequences may be used for the CRC mask for the methoddepicted in FIG. 5 .

FIG. 6 is a flowchart diagram which illustrates an example method andprocedure to determine TX/RX beam reciprocity. A TRP or gNB may stillneed to indicate partial TX/RX reciprocity using dynamic signaling suchas Layer 1 (L1)/Layer 2 (L2) signaling. An example procedure as shown inflowchart diagram 600 may be performed to dynamically signal partialTX/RX reciprocity. For example, a WTRU may receive a PBCH indicatingTX/RX beam reciprocity 610. The WTRU may determine if the PBCH indicateseither full TX/RX beam reciprocity or no TX/RX beam reciprocity 620. Ifthe PBCH indicates no TX/RX beam reciprocity, the WTRU may assume no gNBTX/RX beam reciprocity 630. If the PBCH indicates TX/RX beamreciprocity, the WTRU may assume full gNB TX/RX beam reciprocity 640.When the WTRU receives a PBCH indicating full reciprocity, the WTRU maytemporarily assume full gNB TX/RX beam reciprocity 640 until the WTRUreceives a second tier indication indicating whether the gNB TX/RX beamreciprocity is truly full gNB TX/RX beam reciprocity or partial gNBTX/RX beam reciprocity 650. In examples, such a second tier indicationmay be sent using L1/L2 signaling or RRC signaling. The WTRU maydetermine if the second tier indication is for full reciprocity orpartial reciprocity 660. For example, if the second tier indication isfor partial reciprocity, the WTRU may assume partial reciprocity 670.Further, if the second tier indication is for full reciprocity, the WTRUmay assume full reciprocity 680.

In order to indicate three types of association modes, three modes maybe defined. For example, a mode 1 may indicate full association, a mode2 may indicate partial association, and a mode 3 may indicate noassociation. The numbering of the modes may be reordered and still beconsistent with the examples provided herein. Further, different numbersof modes may be used and still be consistent with the examples providedherein.

Three sequences may be used for CRC mask for association mode in thefollowing example method. Association mode may be indicated using CRCmask as well, in an example.

FIG. 7 is a flowchart diagram which illustrates another example methodfor the indication of TX/RX beam reciprocity. In an example shown inflowchart diagram 700, a gNB may generate a PBCH payload 710. Further,the gNB may generate a CRC 730. The generated CRC may be masked with asequence that is a function of the association mode. Depending on thenumber of association modes, a corresponding number of one or more masksmay be used. The generated CRC may be masked by the gNB with a sequencethat is a function of the association mode 750. The PBCH payload andmasked CRC may then be concatenated by the gNB 770.

In a further example, the PBCH CRC may be scrambled or XORed with N bitmask which may jointly indicate number of antennas or antenna ports,antenna configurations antenna and/or TX/RX beam reciprocity. In anexample, N may be 16. In other examples, N may be 8, 24 or 32. If a TRPor gNB has TX/RX reciprocity with M transmit antennas, then the PBCH CRCmay be scrambled with the mask corresponding to TX/RX reciprocity withthe M antennas and so on. A PBCH may also be used to indicate one ormultiple gNB RX beams to WTRU.

The following example method use a PBCH for the indication of a preambleRX beam. In an example for one RX beam indication only, an implicitindication may use a PBCH masking, SS block time index, PBCHdemodulation reference signal (DMRS) sequence index or the like.Further, each mask, SS block time index, PBCH DMRS sequence index or thelike may correspond to the best gNB RX beam. The best gNB RX beam may bemapped to a preamble index, and the mask, SS block time index, and/orPBCH DMRS sequence index may be associated with a preamble index. Thepreamble index may include one or more of a sequence index, time index,frequency index, resource index or the like. In another example, for oneRX beam indication only, an explicit indication may use payload bits,and a few bits may be used to indicate the best gNB RX beam. Forexample, the bits used for explicit indication may be carried in a RACHmessage 2 or an RAR message.

In an example for a multiple RX beam indication, an implicit indicationmay use PBCH masking, SS block time index, PBCH DMRS sequence index orthe like, wherein each mask, SS block time index, PBCH DMRS sequenceindex or the like may correspond to a subset of beams, for example, thebest K gNB RX beam or beams. The best K gNB RX beam(s) may be mapped toa set of one or more preamble indexes and one or more masks, SS blocktime indexes or PBCH DMRS sequence indexes may be associated with a setof preamble indexes. The preamble index may include one or more of asequence index, time index, frequency index, resource index or the like.In an example, the best K gNB RX beam(s) may be mapped to a set of Kpreamble index(es) and K mask(s). In another example for a multiple RXbeam indication, an explicit indication may use payload bits, and a fewbits may be used to indicate a subset of beams, for example, the best KgNB RX beam.

In examples provided herein, a gNB TX beam may be mapped to a gNB RXbeam. In an example, the gNB TX beam may be used to transmit an SS blockwhich may include a time index, which may be an SS block time index.Further a gNB TX beam ID may be an SS block time index. Also, the gNB RXbeam may be used to receive a preamble which may use one or morepreamble sequences and/or one or more preamble resources. Further, thepreamble resources may be allocated according to a preamble resourceindex, which may include a time resource index and/or a frequencyresource index. Also, the preamble sequence may be determined based on apreamble sequence index, In an example, a gNB TX beam may be mapped to atime index x, for example, SS block time index x, and a gNB RX beam maybe mapped to a time index y, for example, PRACH resource time index y.In an example, y may equal x plus c and c may be a time offset, afrequency offset, another type of offset and the like. In furtherexamples, c may be equal to 0 and a time offset may or may not be used.This may imply that the gNB TX beam is associated with the gNB RX beamor a DL SS block time index may be associated with an UL preamble timeresource index. When a WTRU detects the best gNB TX beam at time x, itmay automatically know the best gNB RX beam at time y or vice versa.

When a gNB detects the preamble at time resource index y that istransmitted by a WTRU, it may implicitly know the best SS/PBCH blocktime index x that the WTRU detects. When the WTRU determines to reportsuch a time index say SS/PBCH block time index x to gNB, WTRU may sendpreamble in time resource index y where time index x and y areassociated with each other. In an example, each gNB TX beam may bemapped to an SS block and each gNB RX beam may be mapped to a preambletime resource. In order to ensure that a preamble may be received bygNB's best RX beam, a WTRU should send the preamble at time resource y.When gNB TX/RX reciprocity is not present, the PRACH resource may bedefined by a time-frequency index and the SS block may be associatedwith one or more UL preamble time/frequency resources and/or sequences.For example, the SS block time index may be associated with one or moreUL preamble time/frequency resource and/or sequence index. This isbecause a WTRU can select a preamble and transmit the selected preambleon PRACH time-frequency resources to identify the SS block and feedbackthe SS block time index. For example, a WTRU may select a preamble, suchas preamble index n, and transmit the selected preamble on the PRACHfrequency resources to identify the n-th SS block and feedback the SSblock time index. In another example, a WTRU may select a preamble andtransmit the selected preamble on the PRACH frequency resource, such asresource index n, to identify the n-th SS block and feedback the SSblock time index. In a further example, a WTRU may select a preamble,such as preamble index n, and transmit the selected preamble on thePRACH frequency resource, such as frequency resource index m, toidentify the n-th SS block and feedback the SS block time index. In thiscase, the n-th SS block may be associated with preamble index n andfrequency resource index m.

In an example, a WTRU may select a preamble, such as preamble index n,and transmit the selected preamble on the PRACH frequency resource, suchas frequency resource index m, at a time resource index j to identifythe n-th SS block and feedback the SS block time index. In this case,the n-th SS block may be associated with the preamble index n, frequencyresource index m and time resource index j.

In another example, an SS block may be associated with multiplepreamble, frequency and/or time indexes. In this case a WTRU may selecta preamble in a preamble set, such as preamble set index n, and transmitthe selected preamble on the PRACH frequency resource in a frequencyset, such as frequency resource set index m, at time resource set j toidentify the n-th SS block and feedback the SS block time index. In thiscase, the n-th SS block may be associated with the preamble set index n,frequency resource set index m and/or time resource set index j.

Multiple SS blocks may also be associated with a preamble, frequencyand/or time index. A WTRU may select a preamble, such as preamble indexn, and transmit the selected preamble on the PRACH frequency resource,such as frequency resource index m, at a time resource index j toidentify the n-th set of SS blocks and feedback the SS block time indexor SS block set time index. In this case, the n-th set of SS blocks maybe associated with the preamble index n, frequency resource index mand/or time resource index j.

One or more DL TX beams and one or more UL RX beams may be associated.Association between one or more DL TX beams and one or more UL RX beamsmay be signaled via system information, minimum system information,remaining minimum system information or other system information. SSblock(s), PRACH resource(s), preamble time resources, preamble frequencyresources and/or preamble sequence(s) may each be associated with one ormore of each other. Association between an SS block, a PRACH resourceand/or a preamble sequence may be signaled via system information,minimum system information, remaining minimum system information orother system information.

However, when gNB TX/RX reciprocity is present, the PRACH resources maybe defined by a frequency index only. This is because a WTRU may selecta preamble and transmit the selected preamble on the PRACH frequencyresources at time y to identify the SS block and feedback the SS blocktime index if the PBCH is received at time x. For example, a WTRU mayselect a preamble, such as preamble index n, and transmit the selectedpreamble on the PRACH frequency resource, say frequency resource indexm, at time y to identify the n-th SS block and feedback the SS blocktime index. In this case, the n-th SS block may be associated with thepreamble index n and frequency resource index m. In an example, a WTRUmay not transmit the selected preamble at an undetermined time. A WTRUmay only transmit the selected preamble at the time when the gNB has thebest RX beam present. An advantage in this example may be that thepreamble may be received by gNB using the best RX beam.

In an example, a WTRU may use only a preamble, for example, a preambleresource, sequence, or the like, to report a detected SS/PBCH block. Thepreamble may carry or contain SS/PBCH block information where differentpreambles, such as sequences and/or resources, may indicate differentSS/PBCH blocks. Preamble number x may be used to indicate or reportSS/PBCH block number x. In the examples herein, a preamble may be apreamble sequence, preamble resource or combination of the same. Apreamble resource may be a preamble time resource, frequency resource,preamble spatial resource or combination of the same.

One or more preambles such as one or more preamble sequences and/orresources may be used to indicate or report different SS/PBCH blocks.For example, preamble sequence number x may correspond to SS/PBCH blocknumber x. A WTRU may use preamble sequence number x to indicate orreport SS/PBCH block number x. When a WTRU determines to indicate orreport SS/PBCH block number x, WTRU may select preamble sequence numberx and transmit the selected preamble sequence number x.

In another example, preamble time resource number x may correspond toSS/PBCH block number x. A WTRU may use preamble time resource number xto request SS/PBCH block number x. When a WTRU determines to indicate orreport SS/PBCH block number x, WTRU may select preamble time resourcenumber x and transmit the preamble sequence in preamble time resourcenumber x.

For yet another example, preamble frequency resource number x maycorrespond to SS/PBCH block number x. A WTRU may use preamble frequencyresource number x to indicate or report SS/PBCH block number x. When aWTRU determines to indicate or report SS/PBCH block number x, WTRU mayselect preamble frequency resource number x and transmit the preamblesequence in preamble frequency resource number x.

An association between an SS/PBCH block and a preamble may be used. Anassociation between an SS/PBCH block and a preamble time resource,frequency resource, preamble sequence or any combination of them may beused.

An association between a preamble sequence and an SS/PBCH block may beused. As one example association, one preamble may be associated withone SS/PBCH block. Preamble sequence number x may be associated withSS/PBCH block number x. When a WTRU determines to indicate or reportSS/PBCH block number x, the WTRU may select preamble sequence number xand transmit it. As another example association, one preamble may beassociated with multiple SIBs. Preamble sequence number x may beassociated with SS/PBCH block number x and SS/PBCH block number y. Whena WTRU wants to request SS/PBCH block number x or SS/PBCH block numbery, the WTRU may select preamble sequence number x and transmit it. Asyet another example association, multiple preamble sequences may beassociated with one SS/PBCH block. Preamble sequence number x and numbery may be associated with SS/PBCH block number x. When a WTRU wants torequest SS/PBCH block number x, the WTRU may select preamble sequencenumber x or number y and transmit either Preamble sequence number x ornumber y. WTRU may transmit both Preamble sequence number x and number ywhen multiple preamble sequence transmission is used or enabled.

An association between one or more preamble time resources and one ormore SS/PBCH blocks may be used. As one example association, onepreamble time resource may be associated with one SS/PBCH block.Preamble time resource number x may be associated with SS/PBCH blocknumber x. When WTRU wants to indicate or report SS/PBCH block number x,WTRU may select preamble time resource number x and transmit thepreamble sequence. As another example association, one preamble timeresources may be associated with multiple SIBs. Preamble time resourcenumber x may be associated with SS/PBCH block number x and SS/PBCH blocknumber y. When WTRU wants to indicate or report SS/PBCH block number xor SS/PBCH block number y, WTRU may select preamble time resource numberx and transmit the preamble. As yet another example association,multiple preamble time resources may be associated with one SS/PBCHblock. Preamble time resources number x and number y may be associatedwith SS/PBCH block number x. When WTRU wants to indicate or reportSS/PBCH block number x, WTRU may select preamble time resources number xor number y and transmit the preamble. WTRU may transmit the preamble inboth Preamble time resources number x and number y when multiplepreamble time resources transmission is used or enabled.

Similarly, an association between one or more preamble frequencyresources and one or more SS/PBCH blocks may be used. Likewise, anassociation between any one of one or more preamble time/frequencyresources, one or more sequences and one or more SS/PBCH blocks may beused.

If WTRU receives an indication with the association for a preamble andan SS/PBCH block, WTRU may use the preamble to indicate or report anSS/PBCH block. In an example, the preamble may be a preamble sequence,preamble resource and the like. If WTRU does not receive an indicationwith the association for preamble and SS/PBCH block, WTRU may use acontrol field in a payload, such as a RACH message 3, to indicate orreport the SS/PBCH block.

A single association or mapping may be used. An association indicationof 1 bit may be used. WTRU may be indicated either with or withoutassociation, for example, “1” may indicate “with association” and “0”may indicate “without association”.

In another example, more than one associations or mappings may be used.An association indication of N bits may be used. Two examples may beused. In a one example, two indicators may be used, a first indicatormay indicate with association or without association. In an example, thefirst indicator may be one bit. A second indicator (N bits) may be usedto indicate which association should be used if the WTRU receives thefirst indicator indicating with association. In an example, the secondindicator may be N bits. In another example, a single indicator withjoint coding of “with” and “without” association and multipleassociations. In an example, the single indicator may be N bits. In anexample of 3 associations, a two-bit single indicator may be used.Accordingly, the bits 00 may indicate without association. Further, thebits 01, 10 and 11 may indicate a first association, a secondassociation and a third association, respectively. The firstassociation, the second association and the third association may belabeled “association 1”, “association 2” and “association 3”respectively.

An association indication may be part of a RACH configuration and may becarried or included in a broadcast signal or channel such as a remainingminimum system information (RMSI) signal. The association indication mayalso be carried in a SS, new radio PBCH (NR-PBCH), or other systeminformation (OSI).

The association between SS/PBCH blocks and PRACH preamble (sequence,resource, their indices) may be based on the actually transmittedSS/PBCH blocks which may be indicated in RMSI. In another example, theassociation between SS blocks and PRACH preamble (sequence, resource,their indices) may be based on the maximum SS/PBCH blocks which may bepredetermined according to frequency bands.

The available number of NR-RACH preamble in a cell may be determined byM=L′·K  Equation (1)where L′ may the number of actually transmitted SS-blocks within an SSblock set and K may the number of preambles associated with eachSS-block. In an example, for a one-to-one association of preambles andSS blocks, K may be 1.

The association may be done by mapping the consecutive M preambles in acell to the L′ number of SS-blocks or SS/PBCH blocks. Also, Kconsecutive preambles may be mapped to each SS-block.

The preambles in a cell may be associated or mapped to SS/PBCH blockbased on at least one of the following: cyclic shifts of a rootZadoff-Chu sequence, a root index of the Zadoff-Chu sequence, an NR-RACHpreamble time instances within a slot, a slot index, a frequency index(which may include, for example, a subcarrier index, a PRB index and thelike) and the like.

In an example association, the set of NR-RACH preamble sequences in acell may be determined in the order of the available cyclic shifts of aroot Zadoff-Chu sequence, an increasing NR-RACH preamble time instanceswithin a slot, an increasing root index, an increasing frequency indexand an increasing slot index. In another example, the set of NR-RACHpreamble sequences in a cell may be determined in the order of thecyclic shifts of a root Zadoff-Chu sequence, increasing root index ofZadoff-Chu sequence, increasing NR-RACH preamble time instances within aslot, increasing slot index and increasing frequency index.

A gNB may configure a WTRU to report an additional SS/PBCH block index,for example, a strongest SS/PBCH block index, through a message ofcontention based random access. In an example, the message may be amessage 3 of contention based random access.

The gNB may configure the WTRU to report the multiple SS/PBCH blockindices through a PRACH preamble during a contention-free random accessprocedure, such as, for example, in a handover. The gNB may beconfigured to report the multiple SS/PBCH block indices through one ormore PRACH preambles during a contention-based random access procedure.

In a further example, the best gNB RX beam may be identified without anRX beam sweeping or training at a gNB RX site. This may reduce the beamsweeping or training overhead and latency. The drawback is that PRACHresources may be reduced for a given WTRU because now the WTRU may nothave freedom to use resources of the WTRU's choosing in the time domain.A WTRU may only have freedom in the frequency domain. This may increasetransmission collision probabilities. However, since WTRUs may be forcedto transmit the preamble at different time instances, such preambletransmission may also reduce the collision probabilities for thepreamble transmissions. In case WTRUs are covered by the same beam,WTRUs collision probabilities may be increased since WTRUs may each haveto send a preamble in the same time instance in the same beam withoutspatial separation.

For the WTRUs in different beams, transmission collision may be reducedsince WTRUs are separated in time. This solution may be referred to asautonomous beam scheduling. That is, the time index for a detected bestgNB TX beam may automatically determine the PRACH resources in the timedomain for a WTRU though not in the frequency domain, and the best gNBRX beam may be automatically scheduled. The solution may be consideredto be autonomous TDMA for the RACH.

In an example, the best gNB TX beam may indicate a set of best gNB RXbeams, such as beam set Q. A WTRU may need to send preambles one at atime at time. For example, a WTRU may need to send preambles at timex+nc, time x+nc+1, time x+nc−1 and so on, where n is a positive integerif this beam set is plus and minus the index of the best gNB TX beam.This may be called a local beam set. The local beam set may beconsidered to be local with respect to the index of the best SS/PBCHblock or gNB TX beam.

In another example, a beam set may also be non-local. A WTRU may send apreamble randomly at one or multiple PRACH time resources, such as timex+nc, time x+nc+1, time x+nc−1 and so on. In an example, X may be theindex of the best SS/PBCH block or gNB TX beam, n may be a integernumber and c may be a constant for different designs. Therefore, PRACHresources may be defined by time index, which may be a local time indexand a frequency index, which may be a global frequency index. This localtime index may be local with respect to the index of the best SS/PBCHblock or gNB TX beam. Also, the global frequency index may be globalwith respect to the index of the best SS/PBCH block or gNB TX beam.

FIG. 8 is a flowchart diagram which illustrates an example of a WTRUprocedure for a beam operation mode. As shown in flowchart diagram 800,a WTRU may receive a PBCH at time index x 810. The WTRU may apply a timeoffset to a transmit preamble 830. A WTRU may also receive gNB TX/RXreciprocity indication. The WTRU may determine if the gNB TX/RXreciprocity indication is true or false 850. In an example, if gNB TX/RXreciprocity indicator=TRUE, the WTRU may transmit a preamble at timeindex y, where y=offset+x860. Otherwise the WTRU may transmit a preambleat time index y, where y=offset+x₀ 870.

In an example, a TX/RX beam reciprocity determination, a TX/RX beamrefinement, or both may be performed. For example, a gNB may haveknowledge or information for TX/RX beam reciprocity. A gNB may alsodetermine or refine the TX/RX beam reciprocity by a training method.Such an example solution may be used for, and is not limited to, anexample configuration as follows.

In an example, the best SS/PBCH block may be SS/PBCH block index x andthe best PRACH preamble and/or resource may be PRACH preamblesequence/resource index y. In another example, the best TX beam may bebeam x and the best RX beam may be beam y. In a further exampleconfiguration, y=x, and this may be referred to as full beamreciprocity. In another example configuration, y=x+Δ where Δ=±1, 0, ±2or Δ=±1, ±2, and the like. This is may be referred to as partial beamreciprocity. In an additional example configuration, y≠x and y=x+Δ doesnot hold. This may be referred to as no beam reciprocity.

A beam sweep or training may be used to determine or refine TX/RX beamreciprocity. A multi-stage solution may be used, in example. Forexample, in an example stage, a full beam sweep may be performed. In afurther example stage, TX/RX beam reciprocity may be decided or refined.In another example stage, a power saving beam sweep or training may beperformed to update the beam reciprocity.

In an example, a WTRU TX beam may be mapped to a WTRU RX beam. If a WTRUreceives the PBCH at the best WTRU RX beam z, then the WTRU may send apreamble using the WTRU TX beam z if WTRU TX/RX beam reciprocity ispresent. Otherwise, the WTRU may need to send the preamble by sweepingall WTRU TX beams one at a time at time x+nc where n is a positiveinteger.

In a further example, the best WTRU RX beam may indicate a set of bestWTRU TX beams. In an example, the set of best WTRU TX beams may be abeam set Q. The WTRU may need to send a preamble by sweeping this beamset Q of WTRU TX beams one at a time at time x+nc where n is a positiveinteger. Such a beam set may be predefined, via a master informationblock (MIB)/SIB or via a configuration.

Exemplary methods and procedures for determining beam reciprocity, beamcorrespondence or both are disclosed herein. Beamreciprocity/correspondence for one or more WTRU TX/RX beams may bedetermined via the following example steps. It may be understood to oneskilled in the art that certain steps may be performed out of order ornot performed at all. Other steps may be performed in-between the stepsprovided herein. In step 1, a WTRU may perform TX beam sweeping. In step2, a TRP may determine one or more WTRU TX beams based on a measurementperformed at the TRP. In step 3, the TRP may indicate or transmitinformation regarding the determined WTRU TX beam information based onthe determined one or more WTRU TX beams in step 2. The beam index orbeam indices of the determined one or more beams may be signaled to theWTRU via, but not limited to, RAR, NR-PRACH message 4, NR-PDCCH,NR-enhanced PDCCH (ePDCCH), medium access control element (MAC CE), RRCsignaling or the like.

In step 4, a WTRU may perform RX beam sweeping. In step 5, the WTRU maydetermine one or more RX beams based on one or more measurements. Instep 6, the WTRU may derive TX beam or beams using the determined RXbeam or beams in step 5, assuming beam reciprocity/correspondence at theWTRU. In step 7, the indicated one or more beams in steps 3 and thederived one or more beams in step 6 may be compared at the WTRU, and theWTRU may determine a final beam reciprocity/correspondence at the WTRUbased on a rule or a set of rules. For example, if the indicated andderived beams in steps 3 and 6 are the same, full beamreciprocity/correspondence at the WTRU may be declared and determined.If the indicated and derived beams in steps 3 and 6 are partially thesame, partial beam reciprocity/correspondence at the WTRU may bedeclared and determined. If the indicated and derived beams in steps 3and 6 are totally different, no beam reciprocity/correspondence at theWTRU may be declared and determined.

In order to determine beam reciprocity/correspondence for one or moreTRP TX/RX beams, the following steps may be performed. It may beunderstood to one skilled in the art that certain steps may be performedout of order or not performed at all. Other steps may be performedin-between steps.

In step 1, a TRP may perform TX beam sweeping. In step 2, a WTRU maydetermine one or more TRP TX beams based on one or more measurements. Instep 3, a WTRU may inform, indicate or transmit information regardingthe determined TRP TX beam information based on the determined beam orbeams in step 2. The determined beam index or beam indices may be fedback to the TRP via, but not limited to, WTRU feedback, CSI feedback,NR-PRACH message 1, one or more preambles, NR-PUCCH, NR-PUSCH,scheduling request (SR) or the like.

In step 4, the TRP may perform RX beam sweeping. In step 5, the TRP maydetermine one or more RX beams based on one or more measurements. Instep 6, the TRP may derive TX beam or beams using the determined RX beamor beams in step 5 assuming beam reciprocity/correspondence at the TRP.In step 7, the indicated one or more beams in steps 3 and the derivedone or more beams in step 6 may be compared at the TRP, and the TRP maydetermine final beam reciprocity/correspondence at the TRP based on arule or a set of rules. For example, if the indicated and derived beamsof steps 3 and 6 are the same, full beam reciprocity/correspondence atTRP may be declared and determined. If the indicated and derived beamsof steps 3 and 6 are partially the same, partial beamreciprocity/correspondence at TRP may be declared and determined. If theindicated and derived beams in steps 3 and 6 are totally different, nobeam reciprocity/correspondence at TRP may be declared and determined.

Measurements or metrics to determine beams or beamreciprocity/correspondence may be based on but not limited to signal tonoise ratio (SNR), signal to interference plus noise ratio (SINR),signal strength, power, beam-quality, CSI or the like.

A WTRU beam correspondence or reciprocity may be determined using one ormore of the methods and procedures described herein. Once a WTRU beamcorrespondence or reciprocity has been determined, the results of thedetermined beam correspondence or reciprocity may be signaled orindicated to the other side of the wireless connection. For example, ifa WTRU determines the beam correspondence or reciprocity, the WTRU mayprovide feedback including the results of the determined beamcorrespondence or reciprocity to a gNB, TRP or other WTRU. Such feedbackmay be semi-static or dynamic. For example, the results of a determinedbeam correspondence or reciprocity may be fed back via, but not limitedto, an initial uplink transmission, WTRU feedback, CSI, an NR-PRACHmessage 1, one or more preambles, an NR-PRACH message 3, NR-PUCCH,NR-PUSCH, SR, MAC, MAC CE, RRC signaling, side link transmission or thelike. Such feedback may be either periodic, aperiodic, per request orbased on demand. Such feedback for results of WTRU beam correspondenceor reciprocity may be initiated by the WTRU, TRP or both. Such feedbackfor results of WTRU beam correspondence or reciprocity may be triggeredby an event.

In another example, a WTRU may provide feedback including results of adetermined beam correspondence or reciprocity to a gNB, TRP or otherWTRU as part of a WTRU capability indication. For example, one or moreresults of a determined beam correspondence or reciprocity alone oralong with a WTRU capability may be signaled or indicated to a gNB, TRPor other WTRU, from the given WTRU, via an initial uplink transmission,NR-PRACH message 1, one or more preambles, RRC connection establishmentrequest, NR-PRACH message 3, RRC signaling, side link transmission orthe like.

FIG. 9 is a flowchart diagram which illustrates an example WTRU methodand procedure for determining and reporting WTRU beam correspondence,beam reciprocity or both. In an example shown in flowchart diagram 900,a gNB or TRP may request information for WTRU beam correspondence, beamreciprocity or both 910. A WTRU may perform a method and procedure forbeam correspondence/reciprocity 920. In an example, the WTRU may performthe method and procedure for beam correspondence/reciprocity based onthe request received from the gNB or TRP. In another example, a WTRU mayperform the method and procedure for beam correspondence/reciprocitywithout receiving a request from a gNB or TRP.

Further, the WTRU may send an indication of the beamcorrespondence/reciprocity determination to a gNB or TRP in apredetermined procedure. Such procedure may be via an initial accessprocedure, a random access procedure or RRC procedure during an RRCconnection stage. A WTRU may determine beam correspondence/reciprocityaccording to one or more results of the method and procedure for beamcorrespondence/reciprocity determination 930. In an example, the WTRUmay determine beam correspondence/reciprocity by following a method andprocedure for beam correspondence/reciprocity determination providedelsewhere herein. In an example, a WTRU may indicate information of beamcorrespondence/reciprocity to a gNB or TRP as part of a WTRU capabilityindication 940. A WTRU may also indicate beam correspondence/reciprocityto other WTRUs 950. In an example, the WTRU may also indicate beamcorrespondence/reciprocity to other WTRUs, if necessary.

A WTRU may indicate beam correspondence or reciprocity information to agNB or TRP as part of the WTRU capability transmission. The capabilitytransmission may include full or no beam correspondence or reciprocity,or full, partial or no beam correspondence or reciprocity. Additionalcategories for beam correspondence or reciprocity may also be reported.

In an example, a preamble may be used to indicate a best DL beam for anRAR. A best DL PBCH beam may be used for an RAR DL beam if such a DLbeam does not change. Such an association may be done in a synchronousfashion in time (or frequency) at a beam level. However, such anassociation should be within a coherent time. Several reasons may causesuch DL beams for SYNC, PBCH and RAR to change, including: if a channelchange is very fast; if a change due to WTRU rotation or blockageoccurs; if the network decides to use a different DL beam, beamwidth orbeam order; or the like.

Therefore, methods to indicate the best DL beam for RAR are needed insome cases when a gNB changes the beam sweep order for an RAR which isdifferent from the beam sweep order for a PBCH. When such association isnot present or not used, an alternative solution may be used. Forexample, a preamble may be used for such an indication.

In an example, a preamble may be used to indicate one of the M DL beams.Different preamble groups may be designed. In this case, a preamble maybe designed with M groups, where each group may indicate one of the M DLbeams. When a WTRU performs random access, the WTRU may select apreamble from the corresponding preamble group associated with thedetected DL beam. When a gNB detects the preamble, may know whichpreamble group the detected preamble belongs to, and thus which DL beammay be used for a following DL transmission, such as for RARtransmission. A DL beam is separated in the spatial domain usually indifferent beam directions, therefore when WTRU selects preamble, theremay be no interference from each other, and no collision may occur. Bothpreambles may be received, and the same random access (RA)-radio networktemporary identifier (RNTI) may be sent.

Further, an RAR message may not collide due to spatial separation. Whentwo or multiple WTRUs detect the same DL beam, and select the samepreamble group, since there are fewer preambles in the smaller group,the likelihood may increase that two WTRUs may select the same preamble,thus collision may occur in RAR. However since the beam is narrow, fewerWTRUs may reside in the same narrow beam, and this may reduce the chancethat multiple WTRUs may initiate the random access procedure. Collisionmay be proportional to the number of WTRUs and inversely proportional tothe number of preambles.

In an example, the number of WTRUs and the number of preambles maycancel out each other in terms of collision probability. In such anexample, the collision probability may remain otherwise the same. Othermethods using a different cyclic shift of the same root sequence,different root sequence or combination of the two may also be used.

In a further example, the indication for WTRU TX/RX beam reciprocity maybe a function of the preamble format such as a long/short format, apreamble sequence length, a preamble group, a preamble sequence, a rootindex, a cyclic shift, one or more frequency/time/spatial resources, orthe like, or a combination of them.

In addition, the indication for the desired TRP TX beam index or indicesmay be a function of preamble format such as a long/short format, apreamble sequence length, a preamble group, a preamble sequence, a rootindex, a cyclic shift, one or more frequency/time/spatial resources, orthe like, or combination of them.

A synchronous design may be simple and incur less overhead, but asynchronous design may offer lower flexibility since a fixed associationis needed and a resource is determined by association. Thus, the fixedassociation and resource determined by association may lowerflexibility. But a synchronous design may reduce the overhead due to theuse of additional signaling for the TX/RX beam reciprocity indication.

A preamble may be used to indicate different service types. By selectinga preamble from one of the M preamble groups, the preamble may indicateeMBB, URLLC, and mMTC, in addition to a DL beam for RAR. A preamble mayalso indicate different combinations of low latency and payload size.

The indication for a service type may be a function of a preamble formatsuch as a long/short format, a preamble sequence length, a preamblegroup, a preamble sequence, a root index, a cyclic shift, one or morefrequency/time/spatial resources, or the like, or combination of them.

In an example, the RA-RNTI may be computed based on the SS/PBCH blockindex associated with the RACH preamble in addition to a slot index anda frequency index in which the preamble was transmitted in time andfrequency.

In another example, the RA-RNTI may also be calculated based on a timeindex and a frequency index. The time index may be a unique value withina RACH resource group. The time index may be a function of a slot indexand a starting symbol index within the slot.

In a further example, time index in the RA-RNTI may be based on one ofthe following: the subframe number, the symbol number, the slot numberand the RACH occasion index within a radio frame.

A RACH resource group may be a set of RACH resources sharing the sameRA-RNTI. A downlink control information (DCI) message in a PDCCHscheduling one or more RAR messages on the PRACH preamble on each of theRACH resources within the RACH resource group may be masked with thesame RA-RNTI. A gNB or network may indicate the number of RACH resourcesper RACH resource group. The gNB or network may indicate the number ofrandom access preamble IDs (RAPIDs). The WTRU may calculate the numberof preambles per RACH resource within a RACH resource group.

One or more PRACH resources may be obtained from a PBCH and/or othersources with and without association. A PBCH may be used to configurebeam resources and PRACH resources, such as, for example, time,frequency, code and the like. Beam resources may also be a part of PRACHresources. Furthermore, a PBCH may be used to jointly configure PRACHresources, such as, for example, time, frequency, code and the like. APBCH may be associated with a PRACH with a synchronous resourcesallocation for the PRACH. By detecting the PBCH DL beam, a WTRU mayobtain the time and beam resources for a preamble transmission. When apreamble group is also associated with beam, by detecting the PBCH DLbeam, a WTRU may also obtain the code resources. In an example, the WTRUobtaining the code resources may include the WTRU obtaining the preamblegroup. A PBCH DL beam may also be associated with frequency resources bymodulo operation.

Synchronous PBCH/PRACH may be designed in two stages. One example stagemay include determining the resources for time, beam and code. Anotherexample stage may include determining frequency resources. If afrequency resource index is denoted as f_(id), the frequency resourcemay be determined by Equation 1:f _(id)=Beam Index mod N _(F)  Equation (2)where N_(F) is the maximum range of f_(id). For example, if 0≤f_(id)<L,then N_(F)=L.

In an example, an asynchronous design may use a dynamic or semi-staticsignaling or combination of the two. In another example, an asynchronousdesign may use a predefined mapping. For example, an angle of departure(AoD), an angle of arrival (AoA) or an overlap beam or beams may be usedas resources. An AoA or an AoD may be estimated during initialsynchronization or PBCH transmission.

A beam sweep method for the next stage may be indicated by the preamble.A beam sweep method may be a function of time, frequency, code, numberof sweeps, number of symbols per sweep, periodicity, and the like.

A PBCH transmission in DL may be associated with PRACH transmission inUL. PBCH-to-PRACH association may be established so that when a WTRUdetects the best PBCH TX beam, it may automatically obtain the knowledgeabout the best preamble gNB RX beam if gNB TX/RX beam reciprocity ispresent. If PBCH transmission is not associated with PRACH transmission,when a WTRU detects the best PBCH TX beam, it may not know the bestpreamble gNB RX beam even if gNB TX/RX beam reciprocity is present.Therefore, the WTRU may need the PBCH to indicate the best preamble gNBRX beam. In another example, a SIB, such as a SIB1, may be used toconfigure preamble and RACH resources.

FIG. 10 is a flowchart diagram which illustrates an example PRACHprocedure and preamble format selection based on beam deployment. In anexample shown in flowchart diagram 1000, the beam deployment may be anindicated beam deployment. As shown in flowchart diagram 1000, a WTRUmay be equipped and/or configured with multiple RACH preamble formats1010. In an example, the RACH preamble formats may include long andshort preamble formats. The WTRU may detect a SYNC signal and receive anindication of single beam or multi-beam operation 1020. Further, theWTRU may determine the preamble format as a function of beam deploymentor beam operation mode 1030. Further, the WTRU may determine whether asingle beam deployment or multi-beam deployment is indicated 1040.

If a single beam deployment or single beam operation mode is indicated,the WTRU may determine the preamble format 1050. Further, the WTRU maytransmit the preamble with the determine preamble length 1055. Then, theWTRU may perform the RACH procedure based on the determined preambleformat 1060. For example, the WTRU may determine a first preambleformat. In an example, the first preamble format may be preamble formatA. In a further example, the WTRU may determine a long preamble formatas preamble format A. Further, the WTRU may transmit the preamble with along preamble length. The WTRU may perform the RACH procedure based onthe determined long preamble format.

If a multi-beam deployment or a multi-beam operation mode is indicated,the WTRU may determine the preamble format 1070. Further, the WTRU maytransmit the preamble with the determine preamble length 1075. Then, theWTRU may perform the RACH procedure based on the determined preambleformat 1080. For example, the WTRU may determine a second preambleformat. In an example, the second preamble format may be preamble formatB. In a further example, the WTRU may determine a short preamble formatas preamble format B. Further, the WTRU may transmit the preamble with ashort preamble length. The WTRU may perform the RACH procedure based onthe determined short preamble format.

FIG. 11 is a flowchart diagram which illustrates another example PRACHprocedure and preamble format selection. As shown in flowchart diagram1100, a WTRU may be equipped and/or configured with multiple RACHpreamble formats, for example, long and short preamble formats 1110. TheWTRU may detect a SYNC signal and receive an indication for multi-beamoperation 1120. Further, the WTRU may measure a DL signal, for example,a SYNC, a PBCH, or a broadcast reference signal (BRS) signal 1130. Also,the WTRU may select a preamble format based on preamble format selectioncriteria 1140. The preamble format selection criteria may include, forexample, a reference signal received power (RSRP), reference signalreceived quality (RSRQ), cell center indication or cell edge indication.The WTRU may determine the long preamble format and transmit thepreamble with long preamble length if RSRP is below a predeterminedthreshold or a cell edge is indicated. Otherwise, the WTRU may determinethe short preamble format and transmit the preamble with short preamblelength.

For example, if a cell edge is indicated, the WTRU may determine thelong preamble format 1150. Further, the WTRU may then transmit thepreamble with long preamble length 1160.

In another example, if a cell center is indicated, the WTRU maydetermine the short preamble format 1170. Further, the WTRU may thentransmit the preamble with short preamble length 1180.

FIG. 12 is a network operation diagram which illustrates a networkoperation mode with an energy saving mode WTRU. As shown in an examplein network operation diagram 1200, when operating in a regular mode1210, a WTRU may perform a full beam sweep. In an example, regular mode1210 may be a first mode. Further, the first mode may be referred to asmode 1. As seen in FIG. 12 , the gNB may transmit and receive usingbeams 1220 and the WTRU may transmit and receive using beams 1230. Whenoperating in an energy efficiency mode 1250, a WTRU may perform a shortbeam sweep or no beam sweep. In this mode, the gNB may transmit andreceive using beams 1260 and the WTRU may transmit and receive usingbeams 1270. In an example, the energy efficiency or low latency mode1250 may be referred to as a second mode. In a further example, thesecond mode may be referred to as mode 2.

Therefore, two operation modes may be needed to achieve energyefficiency. When TX/RX beam reciprocity at WTRU is not present, a gNBand WTRU may operate in mode 1. When TX/RX reciprocity at WTRU ispresent, a gNB and WTRU may operate in mode 2. WTRU may report its TX/RXreciprocity to a gNB in order for the gNB to decide which mode it mayoperate. Each WTRU may report its own TX/RX reciprocity to a gNB, forexample, as part of WTRU capability or as part of CSI feedback. When allWTRUs in a TRP or cell have TX/RX reciprocity, a TRP or a gNB mayconfigure and operate in mode 2 for the TRP or cell. Furthermore whenall WTRUs in a beam have TX/RX beam reciprocity, gNB may configure andoperate in mode 2 for the beam. Therefore a beam, a TRP or a cell mayoperate in either mode 1 or mode 2. In an example, a gNB may switch tomode 2 for energy efficiency when a condition is met. A gNB may switchback to mode 1 for regular operation when a condition is not met.

FIG. 13 is a network operation diagram which illustrates a networkoperation mode with a low latency mode. As shown in an example innetwork operation diagram 1300, a low latency mode 1310 may be used. Inan example, low latency mode 1310 may be a third mode. Further the thirdmode may be referred to as mode 3. As shown in FIG. 13 , the gNB maytransmit and receive using beams 1320 and the WTRU may transmit andreceive using beams 1330.

In an example, when gNB TX/RX reciprocity is present, mode 3 may beused. In mode 3, a gNB may operate an RX period with each gNB RX beamallowing all WTRU TX preamble beams to perform a training with a fullsweep. Because a gNB has TX/RX reciprocity, each WTRU may know when tosend its preamble. Therefore, each WTRU may finish preamble transmissionof all WTRU TX beams in a very short period. Some WTRUs may finishpreamble in a shorter time and some may finish in a longer time,depending on the gNB RX beam for the WTRU. However compared to theregular case where all WTRUs will finish preamble training at the samebut much longer time, mode 3 offers a comparatively lower latencyoperation.

In summary, mode 1 may be operated when no TX/RX beam reciprocity ispresent at both a gNB and an WTRU. Mode 2 may be operated when TX/RXbeam reciprocity is present at the WTRU. Mode 2 may achieve betterenergy savings. Mode 3 may be operated when gNB TX/RX beam reciprocityis present. Mode 3 may achieve low latency operation. When both gNB andWTRU have TX/RX beam reciprocity, an energy efficiency and low latencymode may be used. Such an energy efficiency and low latency mode may bea fourth mode. The fourth mode may be referred to as mode 4.

FIG. 14 is a network operation diagram which illustrates a networkoperation in energy saving mode and low latency mode. As shown in anexample in network operation diagram 1400, an energy saving mode and lowlatency mode 1410 may be used. In an example, energy saving mode and lowlatency mode 1410 may be referred to as mode 4. Mode 4 may achieve bothenergy efficiency and low latency. Further, the gNB may transmit andreceive using beams 1420 and the WTRU may transmit and receive usingbeams 1430.

In an example, in order to make the network operate more efficiently, agNB may indicate an operation mode to the WTRU. For example, threeexample options for such an indication may be used. In an exampleoption, an operation mode may be indicated in a PBCH either explicitlyor implicitly. In another example option, an operation mode may beindicated in a SIB either explicitly or implicitly. In a further exampleoption, an operation mode may be indicated in SYNC either explicitly orimplicitly. In another example, for mode 3, parameter N may bepredefined or configured as a number of WTRU RX beams to participate inan operation.

FIG. 15 is a flowchart diagram which illustrates TRP efficientoperations and determining an operation mode. As shown in an example inflowchart diagram 1500, a WTRU may report the TX/RX beam reciprocityback to the TRP or gNB 1510. Further, the TRP or gNB may collect a WTRUTX/RX beam reciprocity report from all WTRUs in a cell 1530. The TRP orgNB may decide on an appropriate operation mode based on the collectedfeedback for WTRU TX/RX beam reciprocity 1550. The TRP or gNB may signalthe operation mode to the WTRUs 1560.

A simplified RACH procedure using reduced number of steps for randomaccess may be used. A simplified RACH method may be designed as follows.A WTRU may send message X. For example, a WTRU may transmit a preambleand message 3, including an RRC connection request, a WTRU ID, or thelike. Further, a gNB may send message Y. For example, a gNB may send anRAR message with an RRC connection complete message, contentionresolution message, or the like.

When WTRUs send different preambles, no collision of the preamblestypically occurs. Message 3 may be placed on different time/frequencyresources linked to a preamble sequence index.

When WTRUs send the same preamble, a collision may occur. One or more ofthe Message 3s may not be decoded since they are in the sametime/frequency resources. One embodiment includes using differenttime/frequency resources for the preamble by linking message 3 toanother index. For example, time/frequency resources=f(preamble index,other index).

When WTRUs send the same preamble, sometimes a collision may not occurif one WTRU may have much stronger power than the other one or moreWTRUs. In an example, Message 3 for a stronger power WTRU may bedecodable. In this case, a gNB may send a PDCCH masked with a C-RNTI(which may be for the stronger power WTRU ID), and the stronger powerWTRU may decode the PDCCH and a PDSCH accordingly to a received messageY. The other one or more WTRUs in a cell may not decode the PDCCHbecause they use different C-RNTIs (which may be weak power WTRU IDs)and thus cannot decode the PDSCH accordingly. This example approach mayresolve the contention resolution issue.

In examples provided herein, multiple RA procedures may be used. In anexample, a RA procedure may involve the use of a channel that may bereferred to as a RA channel (RACH), for example for sending atransmission. For example, the transmission may be or may include apreamble that may, for example, initiate the RA procedure. An RAprocedure may use another channel and still be consistent with theexamples provided herein. A procedure may be a RA procedure when, forexample, at least one transmission in the procedure may involve therandom selection of at least one parameter on which the transmission maybe based. For example, a RA procedure may involve the random selectionof a transmission parameter. The transmission parameter may be selected,for example, from a set or pool of configured or available candidates.The transmission parameter may be a code, a preamble, a resource, suchas, for example, a time and/or a frequency resource, an identity oridentifier, for example, a WTRU ID, a RNTI, among others, and the like.

In examples, one or more RA procedure types may be used, for examplebased on a WTRU's situation. Different RA procedures may result in adifferent delay, for example, a connection delay or an access delay. AWTRU's situation may, for example, be a mode or a state, for example,idle, connected, suspended, or the like.

A WTRU's situation may, for example, be a capability. A WTRU's situationmay, for example, be a status or a status with respect to a parametersuch as timing advance. A status of a parameter may be whether or not aWTRU has a parameter. A status of a parameter may be an age of theparameter. A WTRU's situation may, for example be a status with respectto a mode such as connected mode. For example, a status, for example,with respect to a mode, may be how long since the WTRU was in a modesuch as connected mode, or how long the WTRU has been asleep or in DRXmode.

In an example, a first type of RA procedure may be referred to as a fullRA procedure and a second type of RA procedure may be referred to as asimplified RA procedure.

A full RA procedure may be used interchangeably with an M-stage RAprocedure, a Type-1 RA procedure, a legacy RA procedure, an LTE RAprocedure, a legacy contention based RA procedure, a legacycontention-free RA procedure and the like.

A simplified RA procedure may be used interchangeably used with anN-stage RA procedure, a Type-2 RA procedure, a new RA procedure, ashortened RA procedure, a low latency RA procedure, a modified RAprocedure and the like.

A full RA procedure may include M, for example, M=4, stages, forexample, steps, wherein a WTRU may receive or transmit, for example, amessage (msg) in a stage. In an example, the WTRU may receive ortransmit a message in each stage.

In an example, a msg may be transmitted by a WTRU. A msg that may betransmitted by a WTRU may be received by an eNode-B. A msg may bereceived by a WTRU, for example from an eNode-B. An eNode-B may be usedas a non-limiting example of a node such as a base station or othernetwork node.

In a non-limiting example, M may be 4. A WTRU may transmit a first msg,for example, Type-1 msg1, in a first stage, for example, stage 1. A WTRUmay receive (or attempt to receive) a second msg, for example, Type-1msg2, in a second stage, for example, stage 2. In a third stage, forexample, stage 3, the WTRU may transmit a third msg, for example, Type-1msg3, for example based on the received second msg. The WTRU may receive(or attempt to receive) a fourth msg, for example, Type-1 msg4) in afourth stage, for example, stage 4). Reception of a Type-1 msg4 mayfinish the RA procedure.

A WTRU may receive, obtain, and/or determine one or more of thefollowing information, for example, during, an RA procedure such as afull RA procedure. The WTRU may receive, obtain, and/or determine atemporary WTRU-ID. Also, the WTRU may receive, obtain, and/or determinea power offset value. Further, the WTRU may receive, obtain, and/ordetermine a timing advance value, such as, for example, an initialtiming advance value. In addition, the WTRU may receive, obtain, and/ordetermine a coverage level. Moreover, the WTRU may receive, obtain,and/or determine a search space, such as a common search space (CSS).Additionally, the WTRU may receive, obtain, and/or determine and/or atleast one configuration, for example, a high layer configuration.

In an example, a temporary WTRU-ID, for example, a C-RNTI, may be usedduring an active mode or state, for example, RRC connected. A temporaryWTRU-ID may be used for uplink and/or downlink transmission, for exampleduring an active state. A temporary WTRU-ID may be used interchangeablywith a C-RNTI, temporary C-RNTI, T-WTRU-ID and the like. A WTRU-ID maybe used interchangeably with IMSI, s-TMSI, P-WTRU-ID and the like. AWTRU-ID may include a T-WTRU-ID, a P-WTRU-ID and the like.

A power offset value, or a transmission power level, may be used, forexample, by the WTRU, for an initial uplink transmission. The poweroffset value may be used when uplink transmission power is calculated atleast for an initial, or first, uplink transmission of data or a controlchannel, for example, when transmitting msg3.

One or more coverage levels may be used, in examples. A coverage levelmay be associated with a set of RA resources or physical RA (PRA)resources. A WTRU may determine a PRA resource for transmission, forexample based on a coverage level it may determine or use. An eNode-B orother receiver of a transmission from a WTRU that may use a PRA resourceand may determine a coverage level of the WTRU, for example, for uplinkand/or downlink transmission, based on the PRA resource.

A WTRU may receive, obtain, and/or determine a search space, forexample, a CSS, of a downlink control channel that the WTRU may use forreceiving, or attempting to receive, a DL control channel, for example,during a RA procedure. For example, one or more CSSs may be used orconfigured and a search space among the configured CSSs may bedetermined based on a coverage level that the WTRU may use. The coveragelevel may be determined, for example, by the WTRU, during RA procedure.Based on the coverage level the WTRU may use for transmission of a RAmsg, the WTRU may monitor a corresponding common search space for a DLcontrol channel that may be associated with a msg, for example, reply,from the eNode-B. The WTRU may use a determined CSS for monitoring of aDL control channel subsequent to completion of an RA procedure.

In a further example, RA resources may be resources for transmission,and/or reception, of signals, channels, and/or messages that may beassociated with a RA procedure. RA resources may be or may include oneor more preambles and/or one or more time/frequency resources, forexample, resources in time and/or frequency.

PRA resources, for example, for a Type-1 msg1, that may be associatedwith a RA procedure, such as a full RA procedure, may be configured,determined, or indicated. Configuration or indication, for example, ofPRA resources for a full RA procedure, may be provided in systeminformation that may be broadcast and/or may be provided in abroadcasting channel. For example, system information may include PRAresources, for example, one or more sets of PRA resources, that may beassociated with a full RA procedures.

A simplified RA procedure may have N, for example, N=2, stages, whereina WTRU may receive or transmit a message (msg) in a stage, for example,each stage. The value of N may be less than the value of M, in anexample. In another example, the value of M may be equal to or less thanthe value of N.

In a non-limiting example, N may be 2. A WTRU may transmit a first msg,for example, Type-2 msg1, in a first stage, for example, stage 1. A WTRUmay receive, or attempt to receive, a second msg, for example, Type-2msg2, in a second stage, for example, stage 2. Reception of a Type-2msg2 may finish the RA procedure.

For a simplified RA procedure, a WTRU may receive, obtain, and/ordetermine a subset of information which may be received, obtained,and/or determined for or from a full RA procedure. For example, duringor as part of a simplified RA procedure, a WTRU may receive, obtain,and/or determine a subset of information which may be received,obtained, and/or determined for or from a full RA procedure.

For example, a WTRU may obtain a T-WTRU-ID during a simplified RAprocedure while the WTRU may obtain a T-WTRU-ID and timing advance valueduring a full RA procedure. In an example, the WTRU obtaining aT-WTRU-ID may be or may include the WTRU receiving the T-WTRU-ID. In afurther example, the WTRU obtaining a T-WTRU-ID may be or may includethe WTRU determining the T-WTRU-ID.

The terms obtain, receive, and determine may be used interchangeably inexamples provided herein. A Type-2 msg1 may be or may include at leastone of: a PRA preamble that may be reserved, configured, or determinedfor a simplified RA procedure; a PRA preamble with, for example, thatmay provide or include, information related to a WTRU-ID; a WTRU-ID;and/or a grant-less transmission such as a grant-less PUSCH, which maybe a GL-PUSCH, transmission.

In an example, a PRA preamble may be a sequence. In an example, a PRApreamble may be a Zadoff-Chu sequence.

In a further example, a PRA preamble may be transmitted in one or morepreamble resources. A PRA preamble may be randomly selected from a setof PRA preambles that may be configured for a simplified RA procedure.

Also, a WTRU-ID may be signalled, for example, using a UL signal thatmay be transmitted in a determined or known time/frequency location. Thetime/frequency location may be determined based on at least one of a PRApreamble, for example, that the WTRU may transmit for at least part ofType-2 msg1, and a WTRU-ID. The WTRU-ID may be at least one ofT-WTRU-ID, P-WTRU-ID, a randomly selected WTRU-ID, and the like. The ULsignal that may be transmitted may be determined as a function of thePRA preamble. The UL signal that may be transmitted may be a known or afixed signal. The UL signal that may be transmitted may be a function ofthe WTRU-ID. The UL signal that may be transmitted may be the PRApreamble.

In an example, a WTRU-ID may be implicitly signaled. For example, aWTRU-ID may be implicitly signaled based on the determination of a PRAresource. In an example, the PRA resource may be a PRA preamble and/ortime/frequency resource. For example, one or more PRA preambles and/orone or more PRA time/frequency resources may be used, determined, and/orconfigured for a simplified RA procedure. A WTRU may transmit a PRApreamble in a PRA time/frequency resource. A PRA preamble and/or a PRAtime/frequency resource may be determined, for example, by the WTRUbased on a WTRU-ID.

In a further example, a WTRU-ID may be transmitted implicitly via adetermined PRA preamble or explicitly via a data resource and/or acontrol resource. A randomly selected WTRU-ID may include an RNTI, forexample, a C-RNTI. For example, a WTRU may randomly select an RNTIwithin a set of RNTIs. The set of RNTIs may be reserved RNTIs and/orconfigured RNTIs. The set of RNTIs may not be used for RRC connectedWTRUs, and/or common functions such as paging, broadcast, RAR, and thelike.

A Type-2 msg1 may be or may include a grant-less transmission such as agrant-less PUSCH transmission. For example, one or more PUSCH types maybe defined including a grant-less PUSCH (GL-PUSCH). A GL-PUSCH maycontain at least one of a data resource, a control resource, and apreamble resource.

A GL-PUSCH, for example, for a Type-2 msg1, may be used, for example, bya WTRU, to send one or more following information. In an example, theGL-PUSCH may be used to send a PRA preamble. Further, the GL-PUSCH maybe used to send a WTRU-ID. Also, the GL-PUSCH may be used to send an RRCconnection request, for example, an RRC connection establishment orreestablishment request. In another example, the GL-PUSCH may be used tosend a coverage level. In an addition example, the GL-PUSCH may be usedto send a service type, for example, an eMBB, an mMTC, a URLLC, and thelike. Moreover, the GL-PUSCH may be used to send a WTRU category ortype, for example, a BL-WTRU, a CE-WTRU, a normal WTRU, or the like.

In an example, an RRC connection request may be transmitted in a dataresource and/or a control resource. Further, a coverage level may beindicated, for example, implicitly, by a determined and/or used GL-PUSCHresource and/or a determined and/or used PRA resource. Also, a servicetype may be a service type requested, required, or needed by the WTRU.

One or more GL-PUSCH resources that may be used for msg1 may beconfigured. In an example, the one or more GL-PUSCH resources may beconfigured via higher layer signalling.

In a further example, a WTRU may receive or attempt to receive a Type-2msg2. For example, a WTRU may monitor a downlink control information(DCI) message in a DL control channel search space for a Type-2 msg2that may be carried in the DCI message. In an example, the controlchannel search space may be a common search space. A DCI message thatmay carry a Type-2 msg2 may be referred to as a DCI-msg2.

The DL control channel search space for a DCI-msg2 may be determinedbased on the uplink resource used for a Type-2 msg1 transmission. Theuplink resource may be determined at least in part based on a WTRU-ID.An RNTI that may be used for a DCI-msg2 may be determined based on theuplink resource used for a Type-2 msg1 transmission and/or the WTRU-ID.

In another example, a WTRU may monitor a DCI message that may indicate adownlink data resource that may carry Type-2 msg2. A Type-2 msg2 mayinclude an indication as to whether a Type-2 msg1 was receivedsuccessfully and/or whether a simplified RA procedure has succeeded. Forexample, a Type-2 msg2 may include a first value, for example, ‘TRUE’,or a second value, for example, ‘FALSE’. The first value may indicatethe confirmation of a WTRU-ID. The first value may indicate thesuccessful reception of a Type-2 msg1 that may be for a particularWTRU-ID. The second value may indicate failure of a simplified RAprocedure.

In an additional example, a Type-2 msg2 may be a signal. For example, asignal may be transmitted to indicate the confirmation of a WTRU-ID thatmay be transmitted implicitly or explicitly by a Type-2 msg1. The signalmay be transmitted to indicate successful reception of a Type-2 msg1that may be for a particular WTRU-ID.

A Type-2 msg2 may carry at least one of following information: a timingadvance value; a power offset for uplink transmission, for example, aninitial uplink transmission; a contention resolution message; an RRCconnection setup complete message; a WTRU-ID or confirmation of WTRU-IDthat may be indicated in or by Type-2 msg1; or one or more higher layerconfigurations. In an example, the information may be provided as aninformation element. In another example, the information may be providedas part of an information element.

In an example solution, one or more types of RA procedures may be usedin a cell. For example, a first RA procedure type and a second RAprocedure type may be used. A first RA procedure type may be a Type-1 orfull RA procedure. A second RA procedure type may be a Type-2 orsimplified RA procedure. A first RA procedure type may be used when afirst WTRU condition may be met and a second RA procedure type may beused when a second WTRU condition may be met.

The number of RA procedure types that may be used, for example, in acell, may be configured, for example by an eNode-B. Two is used hereinas a non-limiting example of a number of RA procedure types that may beused, configured, or indicated, for example by an eNode-B. Any othernumber may be used and still be consistent with the examples providedherein.

For the non-limiting example of two RA procedure types, one or two RAprocedures types may be used, configured, or indicated by an eNode-B. Afirst, for example, Type-1, RA procedure may be used, for example, whenone RA procedure type may be configured or indicated. A first, forexample, Type-1, RA procedure or a second, for example, Type-2, RAprocedure may be used, for example when two RA procedure types may beconfigured or indicated.

In an example, a WTRU may determine a RA procedure type, for example, aType-1 or a Type-2 RA procedure, to use based on one or more offollowing. For example, a WTRU may determine a RA procedure type to usebased on a purpose of the RA procedure, for example, initial access.Further, a WTRU may determine a RA procedure type to use based on a modeor state of the WTRU when performing the RA procedure. Also, a WTRU maydetermine a RA procedure type to use based on whether the WTRU ischanging modes, states, or statuses, for example, from inactive statusto active status, from RRC idle or suspend to RRC connected or resume.In addition, a WTRU may determine a RA procedure type to use based onwhether the WTRU is using the RA procedure to change mode, state orstatus. Moreover, a WTRU may determine a RA procedure type to use basedon a service type, for example, eMBB, URLLC, mMTC, that the WTRU mayneed, use, or request. Additionally, a WTRU may determine a RA proceduretype to use based on a WTRU type or category.

In a further example, a WTRU may determine a RA procedure type, forexample, to use, based on the purpose of the RA procedure, such asinitial access. For example, a WTRU may use a first type, for example,Type-1 or full, RA procedure for initial access. A WTRU may, for exampleperform an initial access after a cell detection or a cell-IDdetermination that may be based on a cell search procedure.

In another example, a WTRU may determine a RA procedure type based onthe mode, state or status of the WTRU. For example, a WTRU may determinea RA procedure type to use based on the mode, state or status of theWTRU. The terms mode, state, and status may be used interchangeably inthe examples provided herein. For example, a WTRU may use a first type,for example, Type-1 or full, RA procedure or a second type, for example,Type-2 or simplified, RA procedure when switching from an inactive, forexample, idle, DRX, or suspended, status to an active, for example,connected or resume, status. Use of Type-1 or Type-2 may be determinedbased on one or more other factors such as how long the WTRU may havebeen in inactive status.

In an additional example, a WTRU may determine a RA procedure type basedon a service type the WTRU may use, request, need, or require. Forexample, a WTRU may determine a RA procedure type to use based on aservice type the WTRU may use, request, need, or require. A WTRU may usea first type, for example, Type-1 or full, RA procedure, for examplewhen a WTRU may use, request, need, or require an eMBB service type. AWTRU may use a second type, for example, Type-2 or a simplified, RAprocedure, for example when a WTRU may use, request, need, or require aURLLC service type.

Further, a WTRU may determine a RA procedure type when switching frominactive status, for example, RRC idle, to active status, for example,RRC connected, based on at least one of the following: an inactivestatus time, a WTRU position, and/or an associated cell-ID, for example,the cell-ID of the cell with which the WTRU may communicate for the RAprocedure. For example, a WTRU may determine a RA procedure type to usewhen switching from inactive status to active status.

In an example, if the inactive status time of a WTRU before it switchesto active status is less than a predefined threshold, a second type, forexample, a Type-2 or a simplified, RA procedure may be used by the WTRU.Otherwise, a first type, for example, Type-1 or full, RA procedure maybe used.

In another example, if a position of a WTRU is changed less than apredefined threshold during inactive status time, a second type, forexample, Type-2 or simplified, RA procedure may be used by the WTRU.Otherwise, a first type, for example, Type-1 or full, RA procedure maybe used.

The WTRU position change may be derived, calculated, measured, ordetermined based on a difference of positions of the WTRU. For example,the difference of positions may be a difference in a position frombefore inactive status, for example, at or near the start of inactivestatus, and a current position when performing the RA procedure or whendetermining which RA procedure type to use. In an example, the positionchange may be derived, calculated, measured, or determined using GPS orobserved time difference of arrival (OTDOA) data.

The WTRU position change may be derived, calculated, measured, ordetermined based on a change in received signal time difference (RSTD)of a signal, for example, a CRS or a PRS. A RSTD may be measured as thedifference of the receive times of a signal from two cells or eNode-Bswhere at least one of the cells or eNode-Bs may be a serving cell oreNode-B of the WTRU. The base value may be a value determined at or nearthe start of inactive status. The current value may be a valuedetermined when performing the RA procedure or when determining which RAprocedure type to use. The change may be the difference between the basevalue and the current value.

In an example, the WTRU position change may be derived, calculated,measured, or determined based on TX-RX time difference drift duringinactive status time. In another example, instead of determining aposition change, a WTRU may use a determination of change in RSTD, forexample, during inactive status, to determine a RA procedure type touse. A second type, for example, Type-2 or simplified, RA procedure maybe used for a determined change below a threshold. A first type, forexample, Type-1 or full, RA procedure may be used for a determinedchange above a threshold.

In an additional example, instead of determining a position change, aWTRU may use a determination of change in TX-RX time difference or TX-RXtime difference drift, for example, during inactive status, to determinea RA procedure type to use. A second type, for example, Type-2 orsimplified, RA procedure may be used for a determined change below athreshold. A first type, for example, Type-1 or full, RA procedure maybe used for a determined change above a threshold.

In another example, if the associated cell-ID is different before andafter inactive status, the WTRU may use a first type, for example, aType-1 or a full, RA procedure. In an example, the associated cell-IDmay be the cell-ID of the serving cell with which the WTRU may perform aRA procedure.

A WTRU may determine a RA procedure type according to one or more of theembodiments or examples described herein. Further, the WTRU may performthe determined RA procedure.

FIG. 16 is a flowchart diagram which illustrates an example method andprocedure for beam reciprocity based random access. Examples shown inflowchart diagram 1600 may also illustrate beam correspondence basedrandom access method and procedure. Beam reciprocity or beamcorrespondence may be indicated by a PBCH with a mask with additionaldetails, for example, RACH timing, in a PBCH payload. For example, a gNBmay generate a PBCH payload 1610. Also, the gNB may generated a CRC1620. Further, the gNB may mask the generated CRC with a sequence thatis a function of TX/RX reciprocity 1630. The PBCH payload may then beconcatenated by the gNB with the masked CRC 1640. The gNB may thentransmit the PBCH payload concatenated by the gNB with the masked CRC.As a result, a WTRU may receive beam reciprocity or beam correspondenceinformation indicated by the PBCH with a mask, the PBCH payload or both1650.

In addition, a WTRU may determine a situation the WTRU or a time valueof the WTRU. The WTRU may determine, for example, a position, beam RSRP,cell ID, state, time since last TA, time in state, or the like. Based onthe situation of the WTRU and/or a time value of the WTRU, for example,situation unchanged, situation change or time value less than athreshold, the WTRU may select different random access methods andprocedures 1670. For example, the WTRU may select as 4-step or 2-steprandom access methods and procedures, or full random or simplifiedrandom access methods and procedures. In an example, when a situation ofthe WTRU is changed, or when a value is greater than or equal to athreshold, the WTRU may select the full four step RACH procedure 1675.In an example, the situation of the WTRU may refer to a position of theWTRU, a beam RSRP, a cell ID, a state of the WTRU, a value of the WTRUwith respect to a threshold and the like. Further, when the situation ischanged or when a value is less than a threshold, the WTRU may selectthe simplified RACH procedure 1680. In an example, the simplified RACHprocedure may be a two step RACH procedure.

The indicated beam reciprocity or beam correspondence informationreceived by the WTRU may be used to determine one or more UL directionsand timing for RACH based on a DL beam and beam reciprocity or beamcorrespondence information 1690. In an example, the one or more ULdirections and timing may be relative to a DL beam.

The WTRU may perform a selected RACH procedure in determined one or moreUL beams based on beam reciprocity information using the determinedtiming 1695, or the like.

Although the example solutions described herein consider LTE, LTE-A, NRor 5G specific protocols, it is understood that the solutions describedherein are not restricted to such protocols or scenarios and areapplicable to other wireless systems or other wireless technologies aswell.

Although features and elements are described above in particularcombinations, one of ordinary skill in the art will appreciate that eachfeature or element can be used alone or in any combination with theother features and elements. In addition, the methods described hereinmay be implemented in a computer program, software, or firmwareincorporated in a computer-readable medium for execution by a computeror processor. Examples of computer-readable media include electronicsignals (transmitted over wired or wireless connections) andcomputer-readable storage media. Examples of computer-readable storagemedia include, but are not limited to, a read only memory (ROM), arandom access memory (RAM), a register, cache memory, semiconductormemory devices, magnetic media such as internal hard disks and removabledisks, magneto-optical media, and optical media such as CD-ROM disks,and digital versatile disks (DVDs). A processor in association withsoftware may be used to implement a radio frequency transceiver for usein a WTRU, UE, terminal, base station, RNC, or any host computer.

What is claimed is:
 1. A wireless transmit/receive unit (WTRU)comprising: a processor configured to: receive a synchronization signal(SS)/physical broadcast channel (PBCH) block transmission; determine anSS/PBCH block index based on information associated with the SS/PBCHblock transmission; determine a physical random access channel (PRACH)resource based on the determined SS/PBCH block index; transmit a firstmessage, the first message comprising a PRACH preamble and a grant-lessphysical uplink shared channel (PUSCH)), wherein the PRACH preamble isassociated with a 2-step random access procedure and the PRACH preambleis transmitted using the determined PRACH resource; and receive a secondmessage in response to the first message, the second message comprisinga contention resolution.
 2. The WTRU of claim 1, wherein the informationassociated with the SS/PBCH block transmission is derived from ademodulation reference signal (DMRS) sequence.
 3. The WTRU of claim 2,wherein the DMRS sequence is transmitted in the SS/PBCH blocktransmission.
 4. The WTRU of claim 1, wherein the information associatedwith the SS/PBCH block transmission is derived from one or more PBCHpayload bits.
 5. The WTRU of claim 1, wherein the SS/PBCH block indexcorresponds to a subset of beams.
 6. The WTRU of claim 5, wherein thesubset of beams comprises a single beam.
 7. The WTRU of claim 6, whereinone or more payload bits are used to indicate the single beam.
 8. TheWTRU of claim 1, wherein the PRACH resource includes one or more ofpreamble resources, time resources and frequency resources.
 9. The WTRUof claim 1, wherein the PRACH resource is determined based on theSS/PBCH index using one or more of a time resource or a frequencyresource.
 10. A method comprising: receiving a synchronization signal(SS)/physical broadcast channel (PBCH) block transmission; determiningan SS/PBCH block index based on information associated with the SS/PBCHblock transmission; determining a physical random access channel (PRACH)resource based on the determined SS/PBCH block index; transmitting afirst message, the first message comprising a PRACH preamble and agrant-less physical uplink shared channel (PUSCH), wherein the PRACHpreamble is associated with a 2-step random access procedure that istransmitted using the determined PRACH resource; and receiving a secondmessage in response to the first message, the second message comprisinga contention resolution.
 11. The method of claim 10, wherein theinformation associated with the SS/PBCH block transmission is derivedfrom a demodulation reference signal (DMRS) sequence.
 12. The method ofclaim 11, wherein the DMRS sequence is transmitted in the SS/PBCH blocktransmission.
 13. The method of claim 10, wherein the informationassociated with the SS/PBCH block transmission is derived from one ormore PBCH payload bits.
 14. The method of claim 10, wherein the SS/PBCHblock index corresponds to a subset of beams.
 15. The method of claim14, wherein the subset of beams comprises a single beam.
 16. The methodof claim 15, wherein one or more payload bits are used to indicate thesingle beam.
 17. The method of claim 10, wherein the PRACH resourceincludes one or more of preamble resources, time resources and frequencyresources.
 18. The method of claim 10, wherein the PRACH resource isdetermined based on the SS/PBCH index using one or more of a timeresource or a frequency resource.
 19. A base station comprising aprocessor configured to: transmit a synchronization signal (SS)/physicalbroadcast channel (PBCH) block transmission; receive a first message,the first message comprising a physical random access channel (PRACH)preamble and a grant-less physical uplink shared channel (PUSCH),wherein the PRACH preamble is associated with a 2-step random accessprocedure and the PRACH preamble is received using a PRACH resource,wherein: the SS/PBCH block transmission is associated with a SS/PBCHblock index, and the SS/PBCH block index is associated with the PRACHresource; and transmit a second message in response to the firstmessage, the second message comprising an indication of contentionresolution.